Add WebView API for smoothScroll

public/platform/Platform.h

 /*
  * Copyright (C) 2012 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 599 matching lines @@
     virtual bool isThreadedCompositingEnabled() { return false; }
 
     virtual WebCompositorSupport* compositorSupport() { return nullptr; }
 
     virtual WebFlingAnimator* createFlingAnimator() { return nullptr; }
 
     // Creates a new fling animation curve instance for device |deviceSource|
     // with |velocity| and already scrolled |cumulativeScroll| pixels.
     virtual WebGestureCurve* createFlingAnimationCurve(WebGestureDevice deviceSource, const WebFloatPoint& velocity, const WebSize& cumulativeScroll) { return nullptr; }
 
+
+    virtual WebGestureCurve* createSmoothScrollAnimationCurve(
+        WebGestureDevice deviceSource, float startX, float startY, float dx, float dy, int64_t duration) { return 0; }
+
     // WebRTC ----------------------------------------------------------
 
     // Creates an WebRTCPeerConnectionHandler for RTCPeerConnection.
     // May return null if WebRTC functionality is not avaliable or out of resources.
     virtual WebRTCPeerConnectionHandler* createRTCPeerConnectionHandler(WebRTCPeerConnectionHandlerClient*) { return nullptr; }
 
     // May return null if WebRTC functionality is not avaliable or out of resources.
     virtual WebMediaStreamCenter* createMediaStreamCenter(WebMediaStreamCenterClient*) { return nullptr; }
 
 
@@ skipping 102 matching lines @@
 protected:
     BLINK_PLATFORM_EXPORT Platform();
     virtual ~Platform() { }
 
     WebThread* m_mainThread;
 };
 
 } // namespace blink
 
 #endif