Reland of Don't change layout size due to top control show/hide

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 944 matching lines @@
 
 bool LayoutView::backgroundIsKnownToBeOpaqueInRect(const LayoutRect&) const
 {
     // FIXME: Remove this main frame check. Same concept applies to subframes too.
     if (!frame()->isMainFrame())
         return false;
 
     return m_frameView->hasOpaqueBackground();
 }
 
-double LayoutView::layoutViewportWidth() const
+FloatSize LayoutView::viewportSizeForViewportUnits() const
 {
-    float scale = m_frameView ? m_frameView->frame().pageZoomFactor() : 1;
-    return viewWidth(IncludeScrollbars) / scale;
-}
-
-double LayoutView::layoutViewportHeight() const
-{
-    float scale = m_frameView ? m_frameView->frame().pageZoomFactor() : 1;
-    return viewHeight(IncludeScrollbars) / scale;
+    return frameView() ? frameView()->viewportSizeForViewportUnits() : FloatSize();
 }
 
 void LayoutView::willBeDestroyed()
 {
     // TODO(wangxianzhu): This is a workaround of crbug.com/570706.
     // Should find and fix the root cause.
     if (PaintLayer* layer = this->layer())
         layer->setNeedsRepaint();
     LayoutBlockFlow::willBeDestroyed();
     m_compositor.clear();
@@ skipping 13 matching lines @@
 }
 
 void LayoutView::sendMediaPositionChangeNotifications(const IntRect& visibleRect)
 {
     for (auto& media : m_mediaForPositionNotification) {
         media->notifyPositionMayHaveChanged(visibleRect);
     }
 }
 
 } // namespace blink