Bug 1434768 - Part 2: Replace nsDocShell::mSessionHistory with ChildSHistory, r=bz

docshell/base/nsDocShell.cpp

@@ -53,6 +53,7 @@
 #include "mozilla/dom/TabChild.h"
 #include "mozilla/dom/TabGroup.h"
 #include "mozilla/dom/ToJSValue.h"
+#include "mozilla/dom/ChildSHistory.h"
 
 
 #include "mozilla/net/ReferrerPolicy.h"
@@ -423,9 +424,8 @@ nsDocShell::~nsDocShell()
 
   Destroy();
 
-  nsCOMPtr<nsISHistoryInternal> shPrivate(do_QueryInterface(mSessionHistory));
+  if (mSessionHistory) {
-  if (shPrivate) {
+    mSessionHistory->LegacySHistoryInternal()->SetRootDocShell(nullptr);
-    shPrivate->SetRootDocShell(nullptr);
   }
 
   if (--gDocShellCount == 0) {
@@ -506,7 +506,8 @@ NS_IMPL_CYCLE_COLLECTION_INHERITED(nsDocShell,
                                    nsDocLoader,
                                    mSessionStorageManager,
                                    mScriptGlobal,
-                                   mInitialClientSource)
+                                   mInitialClientSource,
+                                   mSessionHistory)
 
 NS_IMPL_ADDREF_INHERITED(nsDocShell, nsDocLoader)
 NS_IMPL_RELEASE_INHERITED(nsDocShell, nsDocLoader)
@@ -606,10 +607,11 @@ nsDocShell::GetInterface(const nsIID& aIID, void** aSink)
     return NS_SUCCEEDED(GetAuthPrompt(PROMPT_NORMAL, aIID, aSink)) ?
       NS_OK : NS_NOINTERFACE;
   } else if (aIID.Equals(NS_GET_IID(nsISHistory))) {
-    nsCOMPtr<nsISHistory> shistory;
+    RefPtr<ChildSHistory> shistory = GetSessionHistory();
-    nsresult rv = GetSessionHistory(getter_AddRefs(shistory));
+    if (shistory) {
-    if (NS_SUCCEEDED(rv) && shistory) {
+      // XXX(nika): Stop exposing nsISHistory through GetInterface.
-      shistory.forget(aSink);
+      nsCOMPtr<nsISHistory> legacy = shistory->LegacySHistory();
+      legacy.forget(aSink);
       return NS_OK;
     }
     return NS_NOINTERFACE;
@@ -1164,14 +1166,11 @@ nsDocShell::FirePageHideNotificationInternal(bool aIsUnload,
 
     // If the document is unloading, remove all dynamic subframe entries.
     if (aIsUnload && !aSkipCheckingDynEntries) {
-      nsCOMPtr<nsISHistory> rootSH;
+      RefPtr<ChildSHistory> rootSH = GetRootSessionHistory();
-      GetRootSessionHistory(getter_AddRefs(rootSH));
-      nsCOMPtr<nsISHistoryInternal> shPrivate = do_QueryInterface(rootSH);
       nsCOMPtr<nsISHContainer> container(do_QueryInterface(mOSHE));
-      if (shPrivate && container) {
+      if (rootSH && container) {
-        int32_t index = -1;
+        int32_t index = rootSH->Index();
-        rootSH->GetIndex(&index);
+        rootSH->LegacySHistoryInternal()->RemoveDynEntries(index, container);
-        shPrivate->RemoveDynEntries(index, container);
       }
     }
 
@@ -3992,15 +3991,14 @@ nsDocShell::AddChildSHEntryInternal(nsISHEntry* aCloneRef,
      * and replace the subframe where a new url was loaded with
      * a new entry.
      */
-    int32_t index = -1;
     nsCOMPtr<nsISHEntry> currentHE;
-    mSessionHistory->GetIndex(&index);
+    int32_t index = mSessionHistory->Index();
     if (index < 0) {
       return NS_ERROR_FAILURE;
     }
 
-    rv = mSessionHistory->GetEntryAtIndex(index, false,
+    rv = mSessionHistory->LegacySHistory()->GetEntryAtIndex(
-                                          getter_AddRefs(currentHE));
+      index, false, getter_AddRefs(currentHE));
     NS_ENSURE_TRUE(currentHE, NS_ERROR_FAILURE);
 
     nsCOMPtr<nsISHEntry> currentEntry(do_QueryInterface(currentHE));
@@ -4012,10 +4010,7 @@ nsDocShell::AddChildSHEntryInternal(nsISHEntry* aCloneRef,
         aNewEntry, aCloneChildren, getter_AddRefs(nextEntry));
 
       if (NS_SUCCEEDED(rv)) {
-        nsCOMPtr<nsISHistoryInternal> shPrivate =
+        rv = mSessionHistory->LegacySHistoryInternal()->AddEntry(nextEntry, true);
-          do_QueryInterface(mSessionHistory);
-        NS_ENSURE_TRUE(shPrivate, NS_ERROR_FAILURE);
-        rv = shPrivate->AddEntry(nextEntry, true);
       }
     }
   } else {
@@ -4043,10 +4038,9 @@ nsDocShell::AddChildSHEntryToParent(nsISHEntry* aNewEntry, int32_t aChildOffset,
 
   // In this case, we will end up calling AddEntry, which increases the
   // current index by 1
-  nsCOMPtr<nsISHistory> rootSH;
+  RefPtr<ChildSHistory> rootSH = GetRootSessionHistory();
-  GetRootSessionHistory(getter_AddRefs(rootSH));
   if (rootSH) {
-    rootSH->GetIndex(&mPreviousTransIndex);
+    mPreviousTransIndex = rootSH->Index();
   }
 
   nsresult rv;
@@ -4057,7 +4051,7 @@ nsDocShell::AddChildSHEntryToParent(nsISHEntry* aNewEntry, int32_t aChildOffset,
   }
 
   if (rootSH) {
-    rootSH->GetIndex(&mLoadedTransIndex);
+    mLoadedTransIndex = rootSH->Index();
 #ifdef DEBUG_PAGE_CACHE
     printf("Previous index: %d, Loaded index: %d\n\n", mPreviousTransIndex,
            mLoadedTransIndex);
@@ -4103,25 +4097,19 @@ nsDocShell::GetUseGlobalHistory(bool* aUseGlobalHistory)
 NS_IMETHODIMP
 nsDocShell::RemoveFromSessionHistory()
 {
-  nsCOMPtr<nsISHistoryInternal> internalHistory;
-  nsCOMPtr<nsISHistory> sessionHistory;
   nsCOMPtr<nsIDocShellTreeItem> root;
   GetSameTypeRootTreeItem(getter_AddRefs(root));
-  if (root) {
+  nsCOMPtr<nsIWebNavigation> rootAsWebnav = do_QueryInterface(root);
-    nsCOMPtr<nsIWebNavigation> rootAsWebnav = do_QueryInterface(root);
+  if (!rootAsWebnav) {
-    if (rootAsWebnav) {
-      rootAsWebnav->GetSessionHistory(getter_AddRefs(sessionHistory));
-      internalHistory = do_QueryInterface(sessionHistory);
-    }
-  }
-  if (!internalHistory) {
     return NS_OK;
   }
-
+  RefPtr<ChildSHistory> sessionHistory = rootAsWebnav->GetSessionHistory();
-  int32_t index = 0;
+  if (!sessionHistory) {
-  sessionHistory->GetIndex(&index);
+    return NS_OK;
+  }
+  int32_t index = sessionHistory->Index();
   AutoTArray<nsID, 16> ids({mHistoryID});
-  internalHistory->RemoveEntries(ids, index);
+  sessionHistory->LegacySHistoryInternal()->RemoveEntries(ids, index);
   return NS_OK;
 }
 
@@ -4202,10 +4190,8 @@ void
 nsDocShell::ClearFrameHistory(nsISHEntry* aEntry)
 {
   nsCOMPtr<nsISHContainer> shcontainer = do_QueryInterface(aEntry);
-  nsCOMPtr<nsISHistory> rootSH;
+  RefPtr<ChildSHistory> rootSH = GetRootSessionHistory();
-  GetRootSessionHistory(getter_AddRefs(rootSH));
+  if (!rootSH || !shcontainer) {
-  nsCOMPtr<nsISHistoryInternal> history = do_QueryInterface(rootSH);
-  if (!history || !shcontainer) {
     return;
   }
 
@@ -4219,9 +4205,8 @@ nsDocShell::ClearFrameHistory(nsISHEntry* aEntry)
       ids.AppendElement(child->DocshellID());
     }
   }
-  int32_t index = 0;
+  int32_t index = rootSH->Index();
-  rootSH->GetIndex(&index);
+  rootSH->LegacySHistoryInternal()->RemoveEntries(ids, index);
-  history->RemoveEntries(ids, index);
 }
 
 //-------------------------------------
@@ -4261,33 +4246,31 @@ nsDocShell::IsNavigationAllowed(bool aDisplayPrintErrorDialog,
 NS_IMETHODIMP
 nsDocShell::GetCanGoBack(bool* aCanGoBack)
 {
+  *aCanGoBack = false;
   if (!IsNavigationAllowed(false)) {
-    *aCanGoBack = false;
     return NS_OK; // JS may not handle returning of an error code
   }
-  nsresult rv;
+  RefPtr<ChildSHistory> rootSH = GetRootSessionHistory();
-  nsCOMPtr<nsISHistory> rootSH;
+  if (rootSH) {
-  rv = GetRootSessionHistory(getter_AddRefs(rootSH));
+    *aCanGoBack = rootSH->CanGo(-1);
-  nsCOMPtr<nsIWebNavigation> webnav(do_QueryInterface(rootSH));
+    return NS_OK;
-  NS_ENSURE_TRUE(webnav, NS_ERROR_FAILURE);
+  }
-  rv = webnav->GetCanGoBack(aCanGoBack);
+  return NS_ERROR_FAILURE;
-  return rv;
 }
 
 NS_IMETHODIMP
 nsDocShell::GetCanGoForward(bool* aCanGoForward)
 {
+  *aCanGoForward = false;
   if (!IsNavigationAllowed(false)) {
-    *aCanGoForward = false;
     return NS_OK; // JS may not handle returning of an error code
   }
-  nsresult rv;
+  RefPtr<ChildSHistory> rootSH = GetRootSessionHistory();
-  nsCOMPtr<nsISHistory> rootSH;
+  if (rootSH) {
-  rv = GetRootSessionHistory(getter_AddRefs(rootSH));
+    *aCanGoForward = rootSH->CanGo(1);
-  nsCOMPtr<nsIWebNavigation> webnav(do_QueryInterface(rootSH));
+    return NS_OK;
-  NS_ENSURE_TRUE(webnav, NS_ERROR_FAILURE);
+  }
-  rv = webnav->GetCanGoForward(aCanGoForward);
+  return NS_ERROR_FAILURE;
-  return rv;
 }
 
 NS_IMETHODIMP
@@ -4296,13 +4279,11 @@ nsDocShell::GoBack()
   if (!IsNavigationAllowed()) {
     return NS_OK; // JS may not handle returning of an error code
   }
-  nsresult rv;
+  RefPtr<ChildSHistory> rootSH = GetRootSessionHistory();
-  nsCOMPtr<nsISHistory> rootSH;
+  NS_ENSURE_TRUE(rootSH, NS_ERROR_FAILURE);
-  rv = GetRootSessionHistory(getter_AddRefs(rootSH));
+  ErrorResult rv;
-  nsCOMPtr<nsIWebNavigation> webnav(do_QueryInterface(rootSH));
+  rootSH->Go(-1, rv);
-  NS_ENSURE_TRUE(webnav, NS_ERROR_FAILURE);
+  return rv.StealNSResult();
-  rv = webnav->GoBack();
-  return rv;
 }
 
 NS_IMETHODIMP
@@ -4311,28 +4292,24 @@ nsDocShell::GoForward()
   if (!IsNavigationAllowed()) {
     return NS_OK; // JS may not handle returning of an error code
   }
-  nsresult rv;
+  RefPtr<ChildSHistory> rootSH = GetRootSessionHistory();
-  nsCOMPtr<nsISHistory> rootSH;
+  NS_ENSURE_TRUE(rootSH, NS_ERROR_FAILURE);
-  rv = GetRootSessionHistory(getter_AddRefs(rootSH));
+  ErrorResult rv;
-  nsCOMPtr<nsIWebNavigation> webnav(do_QueryInterface(rootSH));
+  rootSH->Go(1, rv);
-  NS_ENSURE_TRUE(webnav, NS_ERROR_FAILURE);
+  return rv.StealNSResult();
-  rv = webnav->GoForward();
-  return rv;
 }
 
+// XXX(nika): We may want to stop exposing this API in the child process? Going
+// to a specific index from multiple different processes could definitely race.
 NS_IMETHODIMP
 nsDocShell::GotoIndex(int32_t aIndex)
 {
   if (!IsNavigationAllowed()) {
     return NS_OK; // JS may not handle returning of an error code
   }
-  nsresult rv;
+  RefPtr<ChildSHistory> rootSH = GetRootSessionHistory();
-  nsCOMPtr<nsISHistory> rootSH;
+  NS_ENSURE_TRUE(rootSH, NS_ERROR_FAILURE);
-  rv = GetRootSessionHistory(getter_AddRefs(rootSH));
+  return rootSH->LegacySHistoryWebNav()->GotoIndex(aIndex);
-  nsCOMPtr<nsIWebNavigation> webnav(do_QueryInterface(rootSH));
-  NS_ENSURE_TRUE(webnav, NS_ERROR_FAILURE);
-  rv = webnav->GotoIndex(aIndex);
-  return rv;
 }
 
 NS_IMETHODIMP
@@ -5056,12 +5033,11 @@ nsDocShell::Reload(uint32_t aReloadFlags)
 
   // Send notifications to the HistoryListener if any, about the impending
   // reload
-  nsCOMPtr<nsISHistory> rootSH;
+  RefPtr<ChildSHistory> rootSH = GetRootSessionHistory();
-  rv = GetRootSessionHistory(getter_AddRefs(rootSH));
-  nsCOMPtr<nsISHistoryInternal> shistInt(do_QueryInterface(rootSH));
   bool canReload = true;
   if (rootSH) {
-    shistInt->NotifyOnHistoryReload(mCurrentURI, aReloadFlags, &canReload);
+    rootSH->LegacySHistoryInternal()
+      ->NotifyOnHistoryReload(mCurrentURI, aReloadFlags, &canReload);
   }
 
   if (!canReload) {
@@ -5242,38 +5218,28 @@ nsDocShell::GetReferringURI(nsIURI** aURI)
 }
 
 NS_IMETHODIMP
-nsDocShell::SetSessionHistory(nsISHistory* aSessionHistory)
+nsDocShell::InitSessionHistory()
 {
-  NS_ENSURE_TRUE(aSessionHistory, NS_ERROR_FAILURE);
-  // make sure that we are the root docshell and
-  // set a handle to root docshell in SH.
-
   MOZ_ASSERT(!mIsBeingDestroyed);
 
+  // Make sure that we are the root DocShell, and set a handle to root docshell
+  // in the session history.
   nsCOMPtr<nsIDocShellTreeItem> root;
-  /* Get the root docshell. If *this* is the root docshell
-   * then save a handle to *this* in SH. SH needs it to do
-   * traversions thro' its entries
-   */
   GetSameTypeRootTreeItem(getter_AddRefs(root));
-  NS_ENSURE_TRUE(root, NS_ERROR_FAILURE);
+  if (root != this) {
-  if (root.get() == static_cast<nsIDocShellTreeItem*>(this)) {
+    return NS_ERROR_FAILURE;
-    mSessionHistory = aSessionHistory;
-    nsCOMPtr<nsISHistoryInternal> shPrivate =
-      do_QueryInterface(mSessionHistory);
-    NS_ENSURE_TRUE(shPrivate, NS_ERROR_FAILURE);
-    shPrivate->SetRootDocShell(this);
-    return NS_OK;
   }
-  return NS_ERROR_FAILURE;
+
+  mSessionHistory = new ChildSHistory(this);
+  return NS_OK;
 }
 
 NS_IMETHODIMP
-nsDocShell::GetSessionHistory(nsISHistory** aSessionHistory)
+nsDocShell::GetSessionHistoryXPCOM(nsISupports** aSessionHistory)
 {
   NS_ENSURE_ARG_POINTER(aSessionHistory);
-  *aSessionHistory = mSessionHistory;
+  RefPtr<ChildSHistory> shistory = mSessionHistory;
-  NS_IF_ADDREF(*aSessionHistory);
+  shistory.forget(aSessionHistory);
   return NS_OK;
 }
 
@@ -5529,11 +5495,7 @@ nsDocShell::Destroy()
     // We want to destroy these content viewers now rather than
     // letting their destruction wait for the session history
     // entries to get garbage collected.  (Bug 488394)
-    nsCOMPtr<nsISHistoryInternal> shPrivate =
+    mSessionHistory->LegacySHistoryInternal()->EvictAllContentViewers();
-      do_QueryInterface(mSessionHistory);
-    if (shPrivate) {
-      shPrivate->EvictAllContentViewers();
-    }
     mSessionHistory = nullptr;
   }
 
@@ -8309,13 +8271,11 @@ nsDocShell::RestoreFromHistory()
   mFiredUnloadEvent = false;
 
   mURIResultedInDocument = true;
-  nsCOMPtr<nsISHistory> rootSH;
+  RefPtr<ChildSHistory> rootSH = GetRootSessionHistory();
-  GetRootSessionHistory(getter_AddRefs(rootSH));
   if (rootSH) {
-    nsCOMPtr<nsISHistoryInternal> hist = do_QueryInterface(rootSH);
+    mPreviousTransIndex = rootSH->Index();
-    rootSH->GetIndex(&mPreviousTransIndex);
+    rootSH->LegacySHistoryInternal()->UpdateIndex();
-    hist->UpdateIndex();
+    mLoadedTransIndex = rootSH->Index();
-    rootSH->GetIndex(&mLoadedTransIndex);
 #ifdef DEBUG_PAGE_CACHE
     printf("Previous index: %d, Loaded index: %d\n\n", mPreviousTransIndex,
            mLoadedTransIndex);
@@ -8840,11 +8800,12 @@ nsDocShell::CreateContentViewer(const nsACString& aContentType,
     // EndPageLoad. See bug 302115.
     if (mSessionHistory && !mLSHE) {
       int32_t idx;
-      mSessionHistory->GetRequestedIndex(&idx);
+      mSessionHistory->LegacySHistory()->GetRequestedIndex(&idx);
       if (idx == -1) {
-        mSessionHistory->GetIndex(&idx);
+        idx = mSessionHistory->Index();
       }
-      mSessionHistory->GetEntryAtIndex(idx, false, getter_AddRefs(mLSHE));
+      mSessionHistory->LegacySHistory()->
+        GetEntryAtIndex(idx, false, getter_AddRefs(mLSHE));
     }
 
     mLoadType = LOAD_ERROR_PAGE;
@@ -10109,10 +10070,10 @@ nsDocShell::InternalLoad(nsIURI* aURI,
        * SH menus in go/back/forward buttons won't be empty for this.
        */
       if (mSessionHistory) {
-        int32_t index = -1;
+        int32_t index = mSessionHistory->Index();
-        mSessionHistory->GetIndex(&index);
         nsCOMPtr<nsISHEntry> shEntry;
-        mSessionHistory->GetEntryAtIndex(index, false, getter_AddRefs(shEntry));
+        mSessionHistory->LegacySHistory()->GetEntryAtIndex(
+          index, false, getter_AddRefs(shEntry));
         NS_ENSURE_TRUE(shEntry, NS_ERROR_FAILURE);
         shEntry->SetTitle(mTitle);
       }
@@ -11478,14 +11439,14 @@ nsDocShell::OnNewURI(nsIURI* aURI, nsIChannel* aChannel,
 
   // Create SH Entry (mLSHE) only if there is a SessionHistory object in the
   // current frame or in the root docshell.
-  nsCOMPtr<nsISHistory> rootSH = mSessionHistory;
+  RefPtr<ChildSHistory> rootSH = mSessionHistory;
   if (!rootSH) {
     // Get the handle to SH from the root docshell
-    GetRootSessionHistory(getter_AddRefs(rootSH));
+    rootSH = GetRootSessionHistory();
-    if (!rootSH) {
+  }
-      updateSHistory = false;
+  if (!rootSH) {
-      updateGHistory = false; // XXX Why global history too?
+    updateSHistory = false;
-    }
+    updateGHistory = false; // XXX Why global history too?
   }
 
   // Check if the url to be loaded is the same as the one already loaded.
@@ -11598,16 +11559,15 @@ nsDocShell::OnNewURI(nsIURI* aURI, nsIChannel* aChannel,
     // Even if we don't add anything to SHistory, ensure the current index
     // points to the same SHEntry as our mLSHE.
     int32_t index = 0;
-    mSessionHistory->GetRequestedIndex(&index);
+    mSessionHistory->LegacySHistory()->GetRequestedIndex(&index);
     if (index == -1) {
-      mSessionHistory->GetIndex(&index);
+      index = mSessionHistory->Index();
     }
     nsCOMPtr<nsISHEntry> currentSH;
-    mSessionHistory->GetEntryAtIndex(index, false, getter_AddRefs(currentSH));
+    mSessionHistory->LegacySHistory()->GetEntryAtIndex(
+      index, false, getter_AddRefs(currentSH));
     if (currentSH != mLSHE) {
-      nsCOMPtr<nsISHistoryInternal> shPrivate =
+      mSessionHistory->LegacySHistoryInternal()->ReplaceEntry(index, mLSHE);
-        do_QueryInterface(mSessionHistory);
-      shPrivate->ReplaceEntry(index, mLSHE);
     }
   }
 
@@ -11639,16 +11599,13 @@ nsDocShell::OnNewURI(nsIURI* aURI, nsIChannel* aChannel,
   if (rootSH &&
        ((mLoadType & (LOAD_CMD_HISTORY | LOAD_CMD_RELOAD)) ||
          mLoadType == LOAD_NORMAL_REPLACE)) {
-    nsCOMPtr<nsISHistoryInternal> shInternal(do_QueryInterface(rootSH));
+    mPreviousTransIndex = rootSH->Index();
-    if (shInternal) {
+    rootSH->LegacySHistoryInternal()->UpdateIndex();
-      rootSH->GetIndex(&mPreviousTransIndex);
+    mLoadedTransIndex = rootSH->Index();
-      shInternal->UpdateIndex();
-      rootSH->GetIndex(&mLoadedTransIndex);
 #ifdef DEBUG_PAGE_CACHE
-      printf("Previous index: %d, Loaded index: %d\n\n",
+    printf("Previous index: %d, Loaded index: %d\n\n",
-             mPreviousTransIndex, mLoadedTransIndex);
+           mPreviousTransIndex, mLoadedTransIndex);
 #endif
-    }
   }
 
   // aCloneSHChildren exactly means "we are not loading a new document".
@@ -11949,26 +11906,19 @@ nsDocShell::AddState(JS::Handle<JS::Value> aData, const nsAString& aTitle,
   // the history so it can evict content viewers if appropriate. Otherwise
   // call ReplaceEntry so that we notify nsIHistoryListeners that an entry
   // was replaced.
-  nsCOMPtr<nsISHistory> rootSH;
+  RefPtr<ChildSHistory> rootSH = GetRootSessionHistory();
-  GetRootSessionHistory(getter_AddRefs(rootSH));
-  NS_ENSURE_TRUE(rootSH, NS_ERROR_UNEXPECTED);
-
-  nsCOMPtr<nsISHistoryInternal> internalSH = do_QueryInterface(rootSH);
-  NS_ENSURE_TRUE(internalSH, NS_ERROR_UNEXPECTED);
-
   if (!aReplace) {
-    int32_t curIndex = -1;
+    int32_t curIndex = rootSH->Index();
-    rv = rootSH->GetIndex(&curIndex);
+    if (curIndex > -1) {
-    if (NS_SUCCEEDED(rv) && curIndex > -1) {
+      rootSH->LegacySHistoryInternal()->EvictOutOfRangeContentViewers(curIndex);
-      internalSH->EvictOutOfRangeContentViewers(curIndex);
     }
   } else {
     nsCOMPtr<nsISHEntry> rootSHEntry = nsSHistory::GetRootSHEntry(newSHEntry);
 
     int32_t index = -1;
-    rv = rootSH->GetIndexOfEntry(rootSHEntry, &index);
+    rv = rootSH->LegacySHistory()->GetIndexOfEntry(rootSHEntry, &index);
     if (NS_SUCCEEDED(rv) && index > -1) {
-      internalSH->ReplaceEntry(index, rootSHEntry);
+      rootSH->LegacySHistoryInternal()->ReplaceEntry(index, rootSHEntry);
     }
   }
 
@@ -12276,17 +12226,15 @@ nsDocShell::AddToSessionHistory(nsIURI* aURI, nsIChannel* aChannel,
       // valid, it indicates the loading was triggered by a history load, and
       // we should replace the entry at requested index instead.
       int32_t index = 0;
-      mSessionHistory->GetRequestedIndex(&index);
+      mSessionHistory->LegacySHistory()->GetRequestedIndex(&index);
       if (index == -1) {
-        mSessionHistory->GetIndex(&index);
+        index = mSessionHistory->Index();
       }
-      nsCOMPtr<nsISHistoryInternal> shPrivate =
+
-        do_QueryInterface(mSessionHistory);
       // Replace the current entry with the new entry
       if (index >= 0) {
-        if (shPrivate) {
+        rv = mSessionHistory->LegacySHistoryInternal()->ReplaceEntry(index,
-          rv = shPrivate->ReplaceEntry(index, entry);
+                                                                     entry);
-        }
       } else {
         // If we're trying to replace an inexistant shistory entry, append.
         addToSHistory = true;
@@ -12295,14 +12243,12 @@ nsDocShell::AddToSessionHistory(nsIURI* aURI, nsIChannel* aChannel,
 
     if (addToSHistory) {
       // Add to session history
-      nsCOMPtr<nsISHistoryInternal> shPrivate =
+      mPreviousTransIndex = mSessionHistory->Index();
-        do_QueryInterface(mSessionHistory);
-      NS_ENSURE_TRUE(shPrivate, NS_ERROR_FAILURE);
-      mSessionHistory->GetIndex(&mPreviousTransIndex);
 
       bool shouldPersist = ShouldAddToSessionHistory(aURI, aChannel);
-      rv = shPrivate->AddEntry(entry, shouldPersist);
+      rv = mSessionHistory->LegacySHistoryInternal()->AddEntry(
-      mSessionHistory->GetIndex(&mLoadedTransIndex);
+        entry, shouldPersist);
+      mLoadedTransIndex = mSessionHistory->Index();
 #ifdef DEBUG_PAGE_CACHE
       printf("Previous index: %d, Loaded index: %d\n\n",
              mPreviousTransIndex, mLoadedTransIndex);
@@ -12559,21 +12505,19 @@ nsDocShell::SetHistoryEntry(nsCOMPtr<nsISHEntry>* aPtr, nsISHEntry* aEntry)
   *aPtr = aEntry;
 }
 
-nsresult
+already_AddRefed<ChildSHistory>
-nsDocShell::GetRootSessionHistory(nsISHistory** aReturn)
+nsDocShell::GetRootSessionHistory()
 {
-  nsresult rv;
-
   nsCOMPtr<nsIDocShellTreeItem> root;
-  // Get the root docshell
+  nsresult rv = GetSameTypeRootTreeItem(getter_AddRefs(root));
-  rv = GetSameTypeRootTreeItem(getter_AddRefs(root));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
-  // QI to nsIWebNavigation
+    return nullptr;
-  nsCOMPtr<nsIWebNavigation> rootAsWebnav(do_QueryInterface(root));
-  if (rootAsWebnav) {
-    // Get the handle to SH from the root docshell
-    rv = rootAsWebnav->GetSessionHistory(aReturn);
   }
-  return rv;
+  nsCOMPtr<nsIWebNavigation> webnav = do_QueryInterface(root);
+  if (!webnav) {
+    return nullptr;
+  }
+  return webnav->GetSessionHistory();
 }
 
 nsresult

docshell/base/nsDocShell.h

@@ -17,6 +17,7 @@
 
 #include "mozilla/dom/ProfileTimelineMarkerBinding.h"
 #include "mozilla/gfx/Matrix.h"
+#include "mozilla/dom/ChildSHistory.h"
 
 #include "nsIAuthPromptProvider.h"
 #include "nsIBaseWindow.h"
@@ -874,7 +875,6 @@ private: // member functions
   nsresult PersistLayoutHistoryState();
   nsresult LoadHistoryEntry(nsISHEntry* aEntry, uint32_t aLoadType);
   nsresult SetBaseUrlForWyciwyg(nsIContentViewer* aContentViewer);
-  nsresult GetRootSessionHistory(nsISHistory** aReturn);
   nsresult GetHttpChannel(nsIChannel* aChannel, nsIHttpChannel** aReturn);
   nsresult ConfirmRepost(bool* aRepost);
   nsresult GetPromptAndStringBundle(nsIPrompt** aPrompt,
@@ -883,6 +883,8 @@ private: // member functions
   nsresult SetCurScrollPosEx(int32_t aCurHorizontalPos,
                              int32_t aCurVerticalPos);
 
+  already_AddRefed<mozilla::dom::ChildSHistory> GetRootSessionHistory();
+
   inline bool UseErrorPages()
   {
     return (mObserveErrorPages ? sUseErrorPages : mUseErrorPages);
@@ -922,7 +924,7 @@ private: // data members
   nsCOMPtr<nsIDOMStorageManager> mSessionStorageManager;
   nsCOMPtr<nsIContentViewer> mContentViewer;
   nsCOMPtr<nsIWidget> mParentWidget;
-  nsCOMPtr<nsISHistory> mSessionHistory;
+  RefPtr<mozilla::dom::ChildSHistory> mSessionHistory;
   nsCOMPtr<nsIGlobalHistory2> mGlobalHistory;
   nsCOMPtr<nsIWebBrowserFind> mFind;
   nsCOMPtr<nsICommandManager> mCommandManager;

docshell/base/nsIDocShell.idl

@@ -1189,6 +1189,12 @@ interface nsIDocShell : nsIDocShellTreeItem
   void getColorMatrix([optional] out unsigned long aMatrixLen,
                       [array, size_is(aMatrixLen), retval] out float aMatrix);
 
+  /**
+   * Initialize session history for this docshell. The docshell must be the root
+   * docshell.
+   */
+  void initSessionHistory();
+
 %{C++
   /**
    * These methods call nsDocShell::GetHTMLEditorInternal() and

docshell/base/nsIWebNavigation.idl

@@ -10,6 +10,11 @@ interface nsIInputStream;
 interface nsISHistory;
 interface nsIURI;
 interface nsIPrincipal;
+interface nsIChildSHistory;
+
+%{ C++
+#include "mozilla/dom/ChildSHistory.h"
+%}
 
 /**
  * The nsIWebNavigation interface defines an interface for navigating the web.
@@ -374,9 +379,28 @@ interface nsIWebNavigation : nsISupports
   readonly attribute nsIURI referringURI;
 
   /**
-   * The session history object used by this web navigation instance.
+   * The session history object used by this web navigation instance. This
+   * object will be a mozilla::dom::ChildSHistory object, but is returned as
+   * nsISupports so it can be called from JS code.
    */
-  attribute nsISHistory sessionHistory;
+  [binaryname(SessionHistoryXPCOM)]
+  readonly attribute nsISupports sessionHistory;
+
+  %{ C++
+  /**
+   * Get the session history object used by this nsIWebNavigation instance.
+   * Use this method instead of the XPCOM method when getting the
+   * SessionHistory from C++ code.
+   */
+  already_AddRefed<mozilla::dom::ChildSHistory>
+  GetSessionHistory()
+  {
+    nsCOMPtr<nsISupports> history;
+    GetSessionHistoryXPCOM(getter_AddRefs(history));
+    return history.forget()
+      .downcast<mozilla::dom::ChildSHistory>();
+  }
+  %}
 
   /**
    * Set an OriginAttributes dictionary in the docShell. This can be done only

docshell/shistory/ParentSHistory.cpp

@@ -39,12 +39,11 @@ ParentSHistory::GetTabParent()
 already_AddRefed<ChildSHistory>
 ParentSHistory::GetChildIfSameProcess()
 {
-  if (XRE_IsContentProcess()) {
+  if (GetDocShell()) {
-    MOZ_ASSERT(!mDocShell);
+    return GetDocShell()->GetSessionHistory();
-    return nullptr;
   }
 
-  MOZ_CRASH("Unimplemented!");
+  return nullptr;
 }
 
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(ParentSHistory)

docshell/shistory/nsSHistory.cpp

@@ -1789,15 +1789,9 @@ nsSHistory::GetReferringURI(nsIURI** aURI)
 }
 
 NS_IMETHODIMP
-nsSHistory::SetSessionHistory(nsISHistory* aSessionHistory)
+nsSHistory::GetSessionHistoryXPCOM(nsISupports** aSessionHistory)
-{
-  // Not implemented
-  return NS_OK;
-}
-
-NS_IMETHODIMP
-nsSHistory::GetSessionHistory(nsISHistory** aSessionHistory)
 {
+  *aSessionHistory = nullptr;
   // Not implemented
   return NS_OK;
 }

dom/base/nsCCUncollectableMarker.cpp

@@ -255,14 +255,13 @@ MarkDocShell(nsIDocShellTreeItem* aNode, bool aCleanupJS)
   MarkContentViewer(cview, aCleanupJS);
 
   nsCOMPtr<nsIWebNavigation> webNav = do_QueryInterface(shell);
-  nsCOMPtr<nsISHistory> history;
+  RefPtr<ChildSHistory> history = webNav->GetSessionHistory();
-  webNav->GetSessionHistory(getter_AddRefs(history));
   if (history) {
-    int32_t i, historyCount;
+    int32_t historyCount = history->Count();
-    history->GetCount(&historyCount);
+    for (int32_t i = 0; i < historyCount; ++i) {
-    for (i = 0; i < historyCount; ++i) {
       nsCOMPtr<nsISHEntry> shEntry;
-      history->GetEntryAtIndex(i, false, getter_AddRefs(shEntry));
+      history->LegacySHistory()->GetEntryAtIndex(
+        i, false, getter_AddRefs(shEntry));
 
       MarkSHEntry(shEntry, aCleanupJS);
     }

dom/base/nsFrameLoader.cpp

@@ -98,6 +98,8 @@
 #include "mozilla/dom/Promise.h"
 #include "mozilla/dom/PromiseNativeHandler.h"
 #include "mozilla/dom/GroupedHistoryEvent.h"
+#include "mozilla/dom/ParentSHistory.h"
+#include "mozilla/dom/ChildSHistory.h"
 
 #include "mozilla/dom/HTMLBodyElement.h"
 
@@ -1376,10 +1378,8 @@ nsFrameLoader::SwapWithOtherLoader(nsFrameLoader* aOther,
     return NS_ERROR_NOT_IMPLEMENTED;
   }
 
-  nsCOMPtr<nsISHistory> ourHistory;
+  RefPtr<ChildSHistory> ourHistory = ourRootWebnav->GetSessionHistory();
-  nsCOMPtr<nsISHistory> otherHistory;
+  RefPtr<ChildSHistory> otherHistory = otherRootWebnav->GetSessionHistory();
-  ourRootWebnav->GetSessionHistory(getter_AddRefs(ourHistory));
-  otherRootWebnav->GetSessionHistory(getter_AddRefs(otherHistory));
 
   if ((ourRootTreeItem != ourDocshell || otherRootTreeItem != otherDocshell) &&
       (ourHistory || otherHistory)) {
@@ -1609,15 +1609,11 @@ nsFrameLoader::SwapWithOtherLoader(nsFrameLoader* aOther,
   aOtherOwner->InternalSetFrameLoader(kungFuDeathGrip);
 
   // Drop any cached content viewers in the two session histories.
-  nsCOMPtr<nsISHistoryInternal> ourInternalHistory =
+  if (ourHistory) {
-    do_QueryInterface(ourHistory);
+    ourHistory->LegacySHistoryInternal()->EvictAllContentViewers();
-  nsCOMPtr<nsISHistoryInternal> otherInternalHistory =
-    do_QueryInterface(otherHistory);
-  if (ourInternalHistory) {
-    ourInternalHistory->EvictAllContentViewers();
   }
-  if (otherInternalHistory) {
+  if (otherHistory) {
-    otherInternalHistory->EvictAllContentViewers();
+    otherHistory->LegacySHistoryInternal()->EvictAllContentViewers();
   }
 
   NS_ASSERTION(ourFrame == ourContent->GetPrimaryFrame() &&
@@ -2110,13 +2106,9 @@ nsFrameLoader::MaybeCreateDocShell()
   if (mIsTopLevelContent &&
       mOwnerContent->IsXULElement(nsGkAtoms::browser) &&
       !mOwnerContent->HasAttr(kNameSpaceID_None, nsGkAtoms::disablehistory)) {
-    nsresult rv;
+    // XXX(nika): Set this up more explicitly?
-    nsCOMPtr<nsISHistory> sessionHistory =
+    nsresult rv = mDocShell->InitSessionHistory();
-      do_CreateInstance(NS_SHISTORY_CONTRACTID, &rv);
     NS_ENSURE_SUCCESS(rv, rv);
-
-    nsCOMPtr<nsIWebNavigation> webNav(do_QueryInterface(mDocShell));
-    webNav->SetSessionHistory(sessionHistory);
   }
 
   OriginAttributes attrs;

dom/base/nsHistory.cpp

@@ -69,22 +69,14 @@ nsHistory::GetLength(ErrorResult& aRv) const
   }
 
   // Get session History from docshell
-  nsCOMPtr<nsISHistory> sHistory = GetSessionHistory();
+  RefPtr<ChildSHistory> sHistory = GetSessionHistory();
   if (!sHistory) {
     aRv.Throw(NS_ERROR_FAILURE);
 
     return 0;
   }
 
-  int32_t len;
+  int32_t len = sHistory->Count();;
-  nsresult rv = sHistory->GetCount(&len);
-
-  if (NS_FAILED(rv)) {
-    aRv.Throw(rv);
-
-    return 0;
-  }
-
   return len >= 0 ? len : 0;
 }
 
@@ -198,26 +190,16 @@ nsHistory::Go(int32_t aDelta, ErrorResult& aRv)
     }
   }
 
-  nsCOMPtr<nsISHistory> session_history = GetSessionHistory();
+  RefPtr<ChildSHistory> session_history = GetSessionHistory();
-  nsCOMPtr<nsIWebNavigation> webnav(do_QueryInterface(session_history));
+  if (!session_history) {
-  if (!webnav) {
     aRv.Throw(NS_ERROR_FAILURE);
 
     return;
   }
 
-  int32_t curIndex = -1;
+  // Ignore the return value from Go(), since returning errors from Go() can
-  int32_t len = 0;
+  // lead to exceptions and a possible leak of history length
-  session_history->GetIndex(&curIndex);
+  session_history->Go(aDelta, IgnoreErrors());
-  session_history->GetCount(&len);
-
-  int32_t index = curIndex + aDelta;
-  if (index > -1 && index < len)
-    webnav->GotoIndex(index);
-
-  // Ignore the return value from GotoIndex(), since returning errors
-  // from GotoIndex() can lead to exceptions and a possible leak
-  // of history length
 }
 
 void
@@ -230,15 +212,14 @@ nsHistory::Back(ErrorResult& aRv)
     return;
   }
 
-  nsCOMPtr<nsISHistory> sHistory = GetSessionHistory();
+  RefPtr<ChildSHistory> sHistory = GetSessionHistory();
-  nsCOMPtr<nsIWebNavigation> webNav(do_QueryInterface(sHistory));
+  if (!sHistory) {
-  if (!webNav) {
     aRv.Throw(NS_ERROR_FAILURE);
 
     return;
   }
 
-  webNav->GoBack();
+  sHistory->Go(-1, IgnoreErrors());
 }
 
 void
@@ -251,15 +232,14 @@ nsHistory::Forward(ErrorResult& aRv)
     return;
   }
 
-  nsCOMPtr<nsISHistory> sHistory = GetSessionHistory();
+  RefPtr<ChildSHistory> sHistory = GetSessionHistory();
-  nsCOMPtr<nsIWebNavigation> webNav(do_QueryInterface(sHistory));
+  if (!sHistory) {
-  if (!webNav) {
     aRv.Throw(NS_ERROR_FAILURE);
 
     return;
   }
 
-  webNav->GoForward();
+  sHistory->Go(1, IgnoreErrors());
 }
 
 void
@@ -322,7 +302,7 @@ nsHistory::GetDocShell() const
   return win->GetDocShell();
 }
 
-already_AddRefed<nsISHistory>
+already_AddRefed<ChildSHistory>
 nsHistory::GetSessionHistory() const
 {
   nsIDocShell *docShell = GetDocShell();
@@ -334,10 +314,6 @@ nsHistory::GetSessionHistory() const
   nsCOMPtr<nsIWebNavigation> webNav(do_QueryInterface(root));
   NS_ENSURE_TRUE(webNav, nullptr);
 
-  nsCOMPtr<nsISHistory> shistory;
-
   // Get SH from nsIWebNavigation
-  webNav->GetSessionHistory(getter_AddRefs(shistory));
+  return webNav->GetSessionHistory();
-
-  return shistory.forget();
 }

dom/base/nsHistory.h

@@ -9,6 +9,7 @@
 #include "mozilla/Attributes.h"
 #include "mozilla/ErrorResult.h"
 #include "mozilla/dom/HistoryBinding.h"
+#include "mozilla/dom/ChildSHistory.h"
 #include "nsCOMPtr.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsPIDOMWindow.h" // for GetParentObject
@@ -59,7 +60,7 @@ protected:
                           const nsAString& aTitle, const nsAString& aUrl,
                           mozilla::ErrorResult& aRv, bool aReplace);
 
-  already_AddRefed<nsISHistory> GetSessionHistory() const;
+  already_AddRefed<mozilla::dom::ChildSHistory> GetSessionHistory() const;
 
   nsCOMPtr<nsIWeakReference> mInnerWindow;
 };

dom/browser-element/BrowserElementChildPreload.js

@@ -139,8 +139,8 @@ BrowserElementChild.prototype = {
 
     let webNavigation = docShell.QueryInterface(Ci.nsIWebNavigation);
     if (!webNavigation.sessionHistory) {
-      webNavigation.sessionHistory = Cc["@mozilla.org/browser/shistory;1"]
+      // XXX(nika): We might need to start this up some other way?
-                                       .createInstance(Ci.nsISHistory);
+      docShell.initSessionHistory();
     }
 
     // This is necessary to get security web progress notifications.

layout/base/nsDocumentViewer.cpp

@@ -2113,10 +2113,8 @@ nsDocumentViewer::Show(void)
       nsCOMPtr<nsIDocShellTreeItem> root;
       treeItem->GetSameTypeRootTreeItem(getter_AddRefs(root));
       nsCOMPtr<nsIWebNavigation> webNav = do_QueryInterface(root);
-      nsCOMPtr<nsISHistory> history;
+      RefPtr<ChildSHistory> history = webNav->GetSessionHistory();
-      webNav->GetSessionHistory(getter_AddRefs(history));
+      if (history) {
-      nsCOMPtr<nsISHistoryInternal> historyInt = do_QueryInterface(history);
-      if (historyInt) {
         int32_t prevIndex,loadedIndex;
         nsCOMPtr<nsIDocShell> docShell = do_QueryInterface(treeItem);
         docShell->GetPreviousTransIndex(&prevIndex);
@@ -2125,7 +2123,8 @@ nsDocumentViewer::Show(void)
         printf("About to evict content viewers: prev=%d, loaded=%d\n",
                prevIndex, loadedIndex);
 #endif
-        historyInt->EvictOutOfRangeContentViewers(loadedIndex);
+        history->LegacySHistoryInternal()->
+          EvictOutOfRangeContentViewers(loadedIndex);
       }
     }
   }

toolkit/components/browser/nsWebBrowser.cpp

@@ -731,30 +731,18 @@ nsWebBrowser::GetReferringURI(nsIURI** aURI)
   return mDocShellAsNav->GetReferringURI(aURI);
 }
 
+// XXX(nika): Consider making the mozilla::dom::ChildSHistory version the
+// canonical one?
 NS_IMETHODIMP
-nsWebBrowser::SetSessionHistory(nsISHistory* aSessionHistory)
+nsWebBrowser::GetSessionHistoryXPCOM(nsISupports** aSessionHistory)
-{
-  if (mDocShell) {
-    return mDocShellAsNav->SetSessionHistory(aSessionHistory);
-  } else {
-    mInitInfo->sessionHistory = aSessionHistory;
-  }
-
-  return NS_OK;
-}
-
-NS_IMETHODIMP
-nsWebBrowser::GetSessionHistory(nsISHistory** aSessionHistory)
 {
   NS_ENSURE_ARG_POINTER(aSessionHistory);
+  *aSessionHistory = nullptr;
   if (mDocShell) {
-    return mDocShellAsNav->GetSessionHistory(aSessionHistory);
+    RefPtr<mozilla::dom::ChildSHistory> shistory =
-  } else {
+      mDocShellAsNav->GetSessionHistory();
-    *aSessionHistory = mInitInfo->sessionHistory;
+    shistory.forget(aSessionHistory);
   }
-
-  NS_IF_ADDREF(*aSessionHistory);
-
   return NS_OK;
 }
 
@@ -1263,11 +1251,7 @@ nsWebBrowser::Create()
   // handler that always gets called (even for subframes) for any bubbling
   // event.
 
-  if (!mInitInfo->sessionHistory) {
+  mDocShell->InitSessionHistory();
-    mInitInfo->sessionHistory = do_CreateInstance(NS_SHISTORY_CONTRACTID, &rv);
-    NS_ENSURE_SUCCESS(rv, rv);
-  }
-  mDocShellAsNav->SetSessionHistory(mInitInfo->sessionHistory);
 
   if (XRE_IsParentProcess()) {
     // Hook up global history. Do not fail if we can't - just warn.

toolkit/components/browser/nsWebBrowser.h

@@ -50,7 +50,6 @@ public:
   int32_t cx;
   int32_t cy;
   bool visible;
-  nsCOMPtr<nsISHistory> sessionHistory;
   nsString name;
 };