Fix main thread top controls scrolling to mirror CC.

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

 /*
  * Copyright (C) 2013 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
@@ skipping 527 matching lines @@
 IntPoint VisualViewport::maximumScrollPosition() const
 {
     return flooredIntPoint(maximumScrollPositionDouble());
 }
 
 DoublePoint VisualViewport::maximumScrollPositionDouble() const
 {
     if (!mainFrame())
         return IntPoint();
 
-    // FIXME: We probably shouldn't be storing the bounds in a float. crbug.com/422331.
+    // TODO(bokan): We probably shouldn't be storing the bounds in a float. crbug.com/470718.
     FloatSize frameViewSize(contentsSize());
 
     if (m_topControlsAdjustment) {
         float minScale = frameHost().pageScaleConstraintsSet().finalConstraints().minimumScale;
         frameViewSize.expand(0, m_topControlsAdjustment / minScale);
     }
 
     frameViewSize.scale(m_scale);
     frameViewSize = FloatSize(flooredIntSize(frameViewSize));
 
     FloatSize viewportSize(m_size);
-    viewportSize.expand(0, m_topControlsAdjustment);
+    viewportSize.expand(0, ceilf(m_topControlsAdjustment));
 
     FloatSize maxPosition = frameViewSize - viewportSize;
     maxPosition.scale(1 / m_scale);
     return DoublePoint(maxPosition);
 }
 
 IntPoint VisualViewport::clampDocumentOffsetAtScale(const IntPoint& offset, float scale)
 {
     if (!mainFrame() || !mainFrame()->view())
         return IntPoint();
@@ skipping 243 matching lines @@
     } else if (graphicsLayer == m_rootTransformLayer) {
         name =  "Root Transform Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace blink