Move middle-click autoscroll to synthetic fling.

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

Index: third_party/WebKit/Source/core/page/ChromeClient.h
diff --git a/third_party/WebKit/Source/core/page/ChromeClient.h b/third_party/WebKit/Source/core/page/ChromeClient.h
index 1d0c1e685592b956d548f664de819e9404946bfc..4fbc05a040aa1c87d614d981deeef8dbeaa8b436 100644
--- a/third_party/WebKit/Source/core/page/ChromeClient.h
+++ b/third_party/WebKit/Source/core/page/ChromeClient.h
@@ -177,6 +177,11 @@ class CORE_EXPORT ChromeClient : public PlatformChromeClient {
   // 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();