Bug 1607984 - P12. Start parent load via DocumentChannel. r=mayhemer,nika,mattwoodrow

Add ParentProcessDocumentChannel object. This object is a DocumentChannel that will start a channel load from the parent process via a DocumentChannel.

The aim of this task is two-fold.
1- Be consistent on how we handle redirects before continuing the load on the final channel.
2- Prepare to initiate a process switch when needed without having to go via an intermediary content process, saving a process switch. This task will be done in a follow-up task.

The behaviour of the ParentProcessDocumentChannel is similar in logic to the DocumentChannelChild/DocumentChannelParent pair.
The ParentProcessDocumentChannel sets up a DocumentLoadListener, have it handle the redirects and upon completion continue the load on the final channel.

Differential Revision: https://phabricator.services.mozilla.com/D70009

docshell/base/nsDocShell.cpp

@@ -73,9 +73,8 @@
 #include "mozilla/dom/nsCSPContext.h"
 #include "mozilla/dom/LoadURIOptionsBinding.h"
 #include "mozilla/dom/JSWindowActorChild.h"
-#include "mozilla/net/DocumentChannel.h"
 #include "nsSHEntry.h"
-#include "mozilla/net/DocumentChannelChild.h"
+#include "mozilla/net/DocumentChannel.h"
 #include "mozilla/net/UrlClassifierFeatureFactory.h"
 #include "ReferrerInfo.h"
 
@@ -5710,7 +5709,8 @@ void nsDocShell::OnRedirectStateChange(nsIChannel* aOldChannel,
   // of redirects handled in the parent process.
   // Query the full redirect chain directly, so that we can add history
   // entries for them.
-  if (RefPtr<DocumentChannel> docChannel = do_QueryObject(aOldChannel)) {
+  RefPtr<DocumentChannel> docChannel = do_QueryObject(aOldChannel);
+  if (docChannel) {
     nsCOMPtr<nsIURI> previousURI;
     uint32_t previousFlags = 0;
     docChannel->GetLastVisit(getter_AddRefs(previousURI), &previousFlags);
@@ -5758,7 +5758,7 @@ void nsDocShell::OnRedirectStateChange(nsIChannel* aOldChannel,
   // check if the new load should go through the application cache.
   nsCOMPtr<nsIApplicationCacheChannel> appCacheChannel =
       do_QueryInterface(aNewChannel);
-  if (appCacheChannel) {
+  if (appCacheChannel && !docChannel) {
     if (GeckoProcessType_Default != XRE_GetProcessType()) {
       // Permission will be checked in the parent process.
       appCacheChannel->SetChooseApplicationCache(true);
@@ -9150,23 +9150,6 @@ static bool IsConsideredSameOriginForUIR(nsIPrincipal* aTriggeringPrincipal,
   return NS_OK;
 }
 
-// Changes here should also be made in
-// E10SUtils.documentChannelPermittedForURI().
-static bool URIUsesDocChannel(nsIURI* aURI) {
-  if (SchemeIsJavascript(aURI) || NS_IsAboutBlank(aURI)) {
-    return false;
-  }
-
-  nsCString spec = aURI->GetSpecOrDefault();
-
-  if (spec.EqualsLiteral("about:printpreview") ||
-      spec.EqualsLiteral("about:crashcontent")) {
-    return false;
-  }
-
-  return true;
-}
-
 /* static */ bool nsDocShell::CreateAndConfigureRealChannelForLoadState(
     BrowsingContext* aBrowsingContext, nsDocShellLoadState* aLoadState,
     LoadInfo* aLoadInfo, nsIInterfaceRequestor* aCallbacks,
@@ -9567,8 +9550,9 @@ nsresult nsDocShell::DoURILoad(nsDocShellLoadState* aLoadState,
   // If we have a pending channel, use the channel we've already created here.
   // We don't need to set up load flags for our channel, as it has already been
   // created.
-  nsCOMPtr<nsIChannel> channel = aLoadState->GetPendingRedirectedChannel();
-  if (channel) {
+
+  if (nsCOMPtr<nsIChannel> channel =
+          aLoadState->GetPendingRedirectedChannel()) {
     MOZ_ASSERT(!aLoadState->HasLoadFlags(INTERNAL_LOAD_FLAGS_IS_SRCDOC),
                "pending channel for srcdoc load?");
 
@@ -9715,20 +9699,11 @@ nsresult nsDocShell::DoURILoad(nsDocShellLoadState* aLoadState,
     cacheKey = mOSHE->GetCacheKey();
   }
 
-  // We want to use DocumentChannel if we're using a supported scheme, or if
-  // we're a sandboxed srcdoc load. Non-sandboxed srcdoc loads need to share
-  // the same principal object as their outer document (and must load in the
-  // same process), which breaks if we serialize to the parent process.
-  bool canUseDocumentChannel =
-      aLoadState->HasLoadFlags(INTERNAL_LOAD_FLAGS_IS_SRCDOC)
-          ? (sandboxFlags & SANDBOXED_ORIGIN)
-          : URIUsesDocChannel(aLoadState->URI());
-
-  if (StaticPrefs::browser_tabs_documentchannel() && XRE_IsContentProcess() &&
-      canUseDocumentChannel) {
-    channel =
-        new DocumentChannelChild(aLoadState, loadInfo, loadFlags, cacheKey);
-    channel->SetNotificationCallbacks(this);
+  nsCOMPtr<nsIChannel> channel;
+  if (DocumentChannel::CanUseDocumentChannel(aLoadState, sandboxFlags)) {
+    channel = DocumentChannel::CreateDocumentChannel(
+        aLoadState, loadInfo, loadFlags, this, sandboxFlags, cacheKey);
+    MOZ_ASSERT(channel);
   } else if (!CreateAndConfigureRealChannelForLoadState(
                  mBrowsingContext, aLoadState, loadInfo, this, this,
                  GetOriginAttributes(), loadFlags, cacheKey, rv,