Bug 851485 - Restoring scroll position from history should only suppress one scroll-to-anchor. r=bzbarsky

layout/base/nsPresShell.cpp

@@ -2890,6 +2890,7 @@ PresShell::GoToAnchor(const nsAString& aAnchorName, bool aScroll)
   if (rootScroll && rootScroll->DidHistoryRestore()) {
     // Scroll position restored from history trumps scrolling to anchor.
     aScroll = false;
+    rootScroll->ClearDidHistoryRestore();
   }
 
   if (content) {

layout/generic/nsGfxScrollFrame.h

@@ -537,6 +537,9 @@ public:
   virtual bool DidHistoryRestore() MOZ_OVERRIDE {
     return mInner.mDidHistoryRestore;
   }
+  virtual void ClearDidHistoryRestore() MOZ_OVERRIDE {
+    mInner.mDidHistoryRestore = false;
+  }
 
   // nsIStatefulFrame
   NS_IMETHOD SaveState(nsPresState** aState) MOZ_OVERRIDE {
@@ -790,6 +793,9 @@ public:
   virtual bool DidHistoryRestore() MOZ_OVERRIDE {
     return mInner.mDidHistoryRestore;
   }
+  virtual void ClearDidHistoryRestore() MOZ_OVERRIDE {
+    mInner.mDidHistoryRestore = false;
+  }
 
   // nsIStatefulFrame
   NS_IMETHOD SaveState(nsPresState** aState) MOZ_OVERRIDE {

layout/generic/nsIScrollableFrame.h

@@ -237,6 +237,12 @@ public:
    * Was the current presentation state for this frame restored from history?
    */
   virtual bool DidHistoryRestore() = 0;
+  /**
+   * Clear the flag so that DidHistoryRestore() returns false until the next
+   * RestoreState call.
+   * @see nsIStatefulFrame::RestoreState
+   */
+  virtual void ClearDidHistoryRestore() = 0;
 };
 
 #endif