Only scroll on main if the targeted frames need to scroll on main

third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights
  * reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@gmail.com>
@@ skipping 1687 matching lines @@
 bool PaintLayerScrollableArea::usesCompositedScrolling() const {
   // See https://codereview.chromium.org/176633003/ for the tests that fail
   // without this disabler.
   DisableCompositingQueryAsserts disabler;
   return layer()->hasCompositedLayerMapping() &&
          layer()->compositedLayerMapping()->scrollingLayer();
 }
 
 bool PaintLayerScrollableArea::shouldScrollOnMainThread() const {
   if (LocalFrame* frame = box().frame()) {
-    if (Page* page = frame->page()) {
-      if (page->scrollingCoordinator()
-              ->shouldUpdateScrollLayerPositionOnMainThread())
-        return true;
-    }
+    if (frame->view()->mainThreadScrollingReasons())
+      return true;
   }
   return ScrollableArea::shouldScrollOnMainThread();
 }
 
 static bool layerNeedsCompositedScrolling(
     PaintLayerScrollableArea::LCDTextMode mode,
     const PaintLayer* layer) {
   if (!layer->scrollsOverflow())
     return false;
 
@@ skipping 291 matching lines @@
 
 void PaintLayerScrollableArea::DelayScrollOffsetClampScope::
     clampScrollableAreas() {
   for (auto& scrollableArea : *s_needsClamp)
     scrollableArea->clampScrollOffsetAfterOverflowChange();
   delete s_needsClamp;
   s_needsClamp = nullptr;
 }
 
 }  // namespace blink