Move middle-click autoscroll to synthetic fling.

third_party/WebKit/Source/core/page/ChromeClient.h

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple, Inc. All rights
  * reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
  * Copyright (C) 2012 Samsung Electronics. All rights reserved.
  *
  * 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.
@@ skipping 159 matching lines @@
   virtual bool TabsToLinks() = 0;
 
   virtual WebViewBase* GetWebView() const = 0;
 
   // Methods used by PlatformChromeClient.
   virtual WebScreenInfo GetScreenInfo() const = 0;
   virtual void SetCursor(const Cursor&, LocalFrame* local_root) = 0;
   // End methods used by PlatformChromeClient.
 
   virtual void SetCursorOverridden(bool) = 0;
+
+  virtual void AutoscrollStart(WebFloatPoint position, LocalFrame*) {}
+  virtual void AutoscrollFling(WebFloatSize velocity, LocalFrame*) {}
+  virtual void AutoscrollEnd(LocalFrame*) {}
+
   virtual Cursor LastSetCursorForTesting() const = 0;
   Node* LastSetTooltipNodeForTesting() const {
     return last_mouse_over_node_.Get();
   }
 
   virtual void SetCursorForPlugin(const WebCursorInfo&, LocalFrame*) = 0;
 
   // Returns a custom visible content rect if a viewport override is active.
   virtual WTF::Optional<IntRect> VisibleContentRectForPainting() const {
     return WTF::nullopt;
@@ skipping 204 matching lines @@
   WeakMember<Node> last_mouse_over_node_;
   LayoutPoint last_tool_tip_point_;
   String last_tool_tip_text_;
 
   FRIEND_TEST_ALL_PREFIXES(ChromeClientTest, SetToolTipFlood);
 };
 
 }  // namespace blink
 
 #endif  // ChromeClient_h