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

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

Index: third_party/WebKit/Source/core/layout/LayoutView.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutView.cpp b/third_party/WebKit/Source/core/layout/LayoutView.cpp
index 6a96778b49ef000ac9f4c4dfac9e611b9f519cdf..88186a58e368e7f72fe904e233c96f6eefafdf0e 100644
--- a/third_party/WebKit/Source/core/layout/LayoutView.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutView.cpp
@@ -962,16 +962,9 @@
     return m_frameView->hasOpaqueBackground();
 }
 
-double LayoutView::layoutViewportWidth() 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;
+FloatSize LayoutView::viewportSizeForViewportUnits() const
+{
+    return frameView() ? frameView()->viewportSizeForViewportUnits() : FloatSize();
 }
 
 void LayoutView::willBeDestroyed()