Tie scroll anchoring adjustments to frame lifecycle instead of layout.

third_party/WebKit/Source/core/layout/LayoutBlock.cpp

Index: third_party/WebKit/Source/core/layout/LayoutBlock.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutBlock.cpp b/third_party/WebKit/Source/core/layout/LayoutBlock.cpp
index 957be040ad0b49d213cc5de46cabd659900de7d3..e9597e14d4703f00d72f9b5c446f7785633387cd 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBlock.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutBlock.cpp
@@ -399,7 +399,7 @@ void LayoutBlock::layout() {
   bool needsScrollAnchoring =
       hasOverflowClip() && getScrollableArea()->shouldPerformScrollAnchoring();
   if (needsScrollAnchoring)
-    getScrollableArea()->scrollAnchor()->save();
+    getScrollableArea()->scrollAnchor()->notifyBeforeLayout();
 
   // Table cells call layoutBlock directly, so don't add any logic here.  Put
   // code into layoutBlock().
@@ -412,16 +412,6 @@ void LayoutBlock::layout() {
     clearLayoutOverflow();
 
   invalidateBackgroundObscurationStatus();
-
-  // If clamping is delayed, we will restore in
-  // PaintLayerScrollableArea::clampScrollPositionsAfterLayout.
-  // Restoring during the intermediate layout may clamp the scroller to the
-  // wrong bounds.
-  bool clampingDelayed = PaintLayerScrollableArea::DelayScrollOffsetClampScope::
-      clampingIsDelayed();
-  if (needsScrollAnchoring && !clampingDelayed)
-    getScrollableArea()->scrollAnchor()->restore();
-
   m_heightAvailableToChildrenChanged = false;
 }