Tie scroll anchoring adjustments to frame lifecycle instead of layout.

third_party/WebKit/Source/core/frame/DOMVisualViewport.cpp

 /*
  * Copyright (C) 2016 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *  * Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  *  * Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 68 matching lines @@
 
 float DOMVisualViewport::pageX() {
   LocalFrame* frame = m_window->frame();
   if (!frame)
     return 0;
 
   FrameView* view = frame->view();
   if (!view)
     return 0;
 
-  frame->document()->updateStyleAndLayoutIgnorePendingStylesheets();
+  frame->document()->updateScrollPosition();
   float viewportX = view->getScrollableArea()->scrollOffset().width();
   return adjustScrollForAbsoluteZoom(viewportX, frame->pageZoomFactor());
 }
 
 float DOMVisualViewport::pageY() {
   LocalFrame* frame = m_window->frame();
   if (!frame)
     return 0;
 
   FrameView* view = frame->view();
   if (!view)
     return 0;
 
-  frame->document()->updateStyleAndLayoutIgnorePendingStylesheets();
+  frame->document()->updateScrollPosition();
   float viewportY = view->getScrollableArea()->scrollOffset().height();
   return adjustScrollForAbsoluteZoom(viewportY, frame->pageZoomFactor());
 }
 
 double DOMVisualViewport::clientWidth() {
   LocalFrame* frame = m_window->frame();
   if (!frame)
     return 0;
 
   if (!frame->isMainFrame()) {
@@ skipping 33 matching lines @@
   if (!frame->isMainFrame())
     return 1;
 
   if (FrameHost* host = m_window->frame()->host())
     return host->visualViewport().pageScale();
 
   return 0;
 }
 
 }  // namespace blink