Don't set shownRatio in main thread top controls on animated state change.

third_party/WebKit/Source/core/frame/TopControls.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef TopControls_h
 #define TopControls_h
 
 #include "core/CoreExport.h"
 #include "platform/heap/Handle.h"
 #include "public/platform/WebTopControlsState.h"
@@ skipping 21 matching lines @@
     // The amount that top controls are currently shown.
     float contentOffset();
 
     float height() const { return m_height; }
     bool shrinkViewport() const { return m_shrinkViewport; }
     void setHeight(float height, bool shrinkViewport);
 
     float shownRatio() const { return m_shownRatio; }
     void setShownRatio(float);
 
-    void updateConstraints(WebTopControlsState constraints);
+    void updateConstraintsAndState(
+        WebTopControlsState constraints,
+        WebTopControlsState current,
+        bool animate);
 
     void scrollBegin();
 
     // Scrolls top controls vertically if possible and returns the remaining scroll
     // amount.
     FloatSize scrollBy(FloatSize scrollDelta);
 
 private:
     explicit TopControls(const FrameHost&);
     void resetBaseline();
@@ skipping 23 matching lines @@
     // controls height.
     bool m_shrinkViewport;
 
     // Constraints on the top controls state
     WebTopControlsState m_permittedState;
 
 };
 } // namespace blink
 
 #endif // TopControls_h