Merge m-c to inbound

docshell/base/nsDocShell.cpp

@@ -755,6 +755,7 @@ nsDocShell::nsDocShell():
     mIsAppTab(false),
     mUseGlobalHistory(false),
     mInPrivateBrowsing(false),
+    mDeviceSizeIsPageSize(false),
     mFiredUnloadEvent(false),
     mEODForCurrentDocument(false),
     mURIResultedInDocument(false),
@@ -3926,6 +3927,27 @@ nsDocShell::GetScriptGlobalObject()
     return mScriptGlobal;
 }
 
+NS_IMETHODIMP
+nsDocShell::SetDeviceSizeIsPageSize(bool aValue)
+{
+    if (mDeviceSizeIsPageSize != aValue) {
+      mDeviceSizeIsPageSize = aValue;
+      nsRefPtr<nsPresContext> presContext;
+      GetPresContext(getter_AddRefs(presContext));
+      if (presContext) {
+          presContext->MediaFeatureValuesChanged(presContext->eAlwaysRebuildStyle);
+      }
+    }
+    return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::GetDeviceSizeIsPageSize(bool* aValue)
+{
+    *aValue = mDeviceSizeIsPageSize;
+    return NS_OK;
+}
+
 void
 nsDocShell::ClearFrameHistory(nsISHEntry* aEntry)
 {
@@ -4935,6 +4957,10 @@ nsDocShell::Create()
         gAddedPreferencesVarCache = true;
     }
 
+    mDeviceSizeIsPageSize =
+        Preferences::GetBool("docshell.device_size_is_page_size",
+                             mDeviceSizeIsPageSize);
+
     nsCOMPtr<nsIObserverService> serv = services::GetObserverService();
     if (serv) {
         const char* msg = mItemType == typeContent ?