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

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2006 Apple Computer, Inc.
  *
  * 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 165 matching lines @@
     // FIXME: This is a work around because the current implementation of counters
     // requires walking the entire tree repeatedly and most pages don't actually use either
     // feature so we shouldn't take the performance hit when not needed. Long term we should
     // rewrite the counter and quotes code.
     void addLayoutCounter() { m_layoutCounterCount++; }
     void removeLayoutCounter() { ASSERT(m_layoutCounterCount > 0); m_layoutCounterCount--; }
     bool hasLayoutCounters() { return m_layoutCounterCount; }
 
     bool backgroundIsKnownToBeOpaqueInRect(const LayoutRect& localRect) const override;
 
-    double layoutViewportWidth() const;
-    double layoutViewportHeight() const;
+    // Returns the viewport size in (CSS pixels) that vh and vw units are calculated from.
+    FloatSize viewportSizeForViewportUnits() const;
 
     void pushLayoutState(LayoutState& layoutState) { m_layoutState = &layoutState; }
     void popLayoutState() { ASSERT(m_layoutState); m_layoutState = m_layoutState->next(); }
     void invalidateTreeIfNeeded(PaintInvalidationState&) final;
 
     LayoutRect visualOverflowRect() const override;
 
     // Invalidates paint for the entire view, including composited descendants, but not including child frames.
     // It is very likely you do not want to call this method.
     void setShouldDoFullPaintInvalidationForViewAndAllDescendants();
@@ skipping 103 matching lines @@
             m_paintInvalidationState->m_cachedOffsetsEnabled = true;
     }
 private:
     const PaintInvalidationState* m_paintInvalidationState;
     bool m_didDisable;
 };
 
 } // namespace blink
 
 #endif // LayoutView_h