Bug 579663. Part 1. Remove unused offset param from GetActiveScrolledRootFor. r=roc

layout/base/FrameLayerBuilder.cpp

@@ -978,12 +978,8 @@ ContainerState::ProcessDisplayItems(const nsDisplayList& aList,
       }
 
       nsIFrame* f = item->GetUnderlyingFrame();
-      nsPoint offsetToActiveScrolledRoot;
       nsIFrame* activeScrolledRoot =
-        nsLayoutUtils::GetActiveScrolledRootFor(f, mBuilder->ReferenceFrame(),
-                                                &offsetToActiveScrolledRoot);
-      NS_ASSERTION(offsetToActiveScrolledRoot == f->GetOffsetToCrossDoc(activeScrolledRoot),
-                   "Wrong offset");
+        nsLayoutUtils::GetActiveScrolledRootFor(f, mBuilder->ReferenceFrame());
       if (item->IsFixedAndCoveringViewport(mBuilder)) {
         // Make its active scrolled root be the active scrolled root of
         // the enclosing viewport, since it shouldn't be scrolled by scrolled
@@ -993,8 +989,7 @@ ContainerState::ProcessDisplayItems(const nsDisplayList& aList,
           nsLayoutUtils::GetClosestFrameOfType(f, nsGkAtoms::viewportFrame);
         NS_ASSERTION(viewportFrame, "no viewport???");
         activeScrolledRoot =
-          nsLayoutUtils::GetActiveScrolledRootFor(viewportFrame, mBuilder->ReferenceFrame(),
-                                                  &offsetToActiveScrolledRoot);
+          nsLayoutUtils::GetActiveScrolledRootFor(viewportFrame, mBuilder->ReferenceFrame());
       }
 
       nscolor uniformColor;

layout/base/nsDisplayList.cpp

@@ -1124,7 +1124,7 @@ PRBool nsDisplayWrapList::ChildrenCanBeInactive(nsDisplayListBuilder* aBuilder,
     nsIFrame* f = i->GetUnderlyingFrame();
     if (f) {
       nsIFrame* activeScrolledRoot =
-        nsLayoutUtils::GetActiveScrolledRootFor(f, nsnull, nsnull);
+        nsLayoutUtils::GetActiveScrolledRootFor(f, nsnull);
       if (activeScrolledRoot != aActiveScrolledRoot)
         return PR_FALSE;
     }
@@ -1248,7 +1248,7 @@ nsDisplayOpacity::GetLayerState(nsDisplayListBuilder* aBuilder,
   if (mFrame->AreLayersMarkedActive())
     return LAYER_ACTIVE;
   nsIFrame* activeScrolledRoot =
-    nsLayoutUtils::GetActiveScrolledRootFor(mFrame, nsnull, nsnull);
+    nsLayoutUtils::GetActiveScrolledRootFor(mFrame, nsnull);
   return !ChildrenCanBeInactive(aBuilder, aManager, mList, activeScrolledRoot)
       ? LAYER_ACTIVE : LAYER_INACTIVE;
 }
@@ -1618,7 +1618,7 @@ nsDisplayTransform::GetLayerState(nsDisplayListBuilder* aBuilder,
   if (mFrame->AreLayersMarkedActive())
     return LAYER_ACTIVE;
   nsIFrame* activeScrolledRoot =
-    nsLayoutUtils::GetActiveScrolledRootFor(mFrame, nsnull, nsnull);
+    nsLayoutUtils::GetActiveScrolledRootFor(mFrame, nsnull);
   return !mStoredList.ChildrenCanBeInactive(aBuilder, 
                                              aManager, 
                                              *mStoredList.GetList(), 

layout/base/nsLayoutUtils.cpp

@@ -680,26 +680,19 @@ nsLayoutUtils::GetScrollableFrameFor(nsIFrame *aScrolledFrame)
 
 nsIFrame*
 nsLayoutUtils::GetActiveScrolledRootFor(nsIFrame* aFrame,
-                                        nsIFrame* aStopAtAncestor,
-                                        nsPoint* aOffset)
+                                        nsIFrame* aStopAtAncestor)
 {
-  nsPoint offset(0,0);
   nsIFrame* f = aFrame;
   while (f != aStopAtAncestor) {
     NS_ASSERTION(!IsPopup(f), "Should have stopped before popup");
-    nsPoint extraOffset(0,0);
-    nsIFrame* parent = GetCrossDocParentFrame(f, &extraOffset);
+    nsIFrame* parent = GetCrossDocParentFrame(f);
     if (!parent)
       break;
     nsIScrollableFrame* sf = do_QueryFrame(parent);
     if (sf && sf->IsScrollingActive() && sf->GetScrolledFrame() == f)
       break;
-    offset += f->GetPosition() + extraOffset;
     f = parent;
   }
-  if (aOffset) {
-    *aOffset = offset;
-  }
   return f;
 }
 

layout/base/nsLayoutUtils.h

@@ -296,12 +296,9 @@ public:
    * such ancestor before we reach aStopAtAncestor in the ancestor chain.
    * We expect frames with the same "active scrolled root" to be
    * scrolled together, so we'll place them in the same ThebesLayer.
-   * @param aOffset the offset from aFrame to the returned frame is stored
-   * here, if non-null
    */
   static nsIFrame* GetActiveScrolledRootFor(nsIFrame* aFrame,
-                                            nsIFrame* aStopAtAncestor,
-                                            nsPoint* aOffset);
+                                            nsIFrame* aStopAtAncestor);
 
   /**
     * GetFrameFor returns the root frame for a view