OverscrollController consumes scroll updates only during gesture-nav.

content/browser/renderer_host/overscroll_controller.h

 // Copyright (c) 2012 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 CONTENT_BROWSER_RENDERER_HOST_OVERSCROLL_CONTROLLER_H_
 #define CONTENT_BROWSER_RENDERER_HOST_OVERSCROLL_CONTROLLER_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "third_party/WebKit/public/web/WebInputEvent.h"
@@ skipping 73 matching lines @@
   // Returns true to indicate that dispatching the event should reset the
   // overscroll gesture status.
   bool DispatchEventResetsState(const blink::WebInputEvent& event) const;
 
   // Processes an event to update the internal state for overscroll. Returns
   // true if the state is updated, false otherwise.
   bool ProcessEventForOverscroll(const blink::WebInputEvent& event);
 
   // Processes horizontal overscroll. This can update both the overscroll mode
   // and the over scroll amount (i.e. |overscroll_mode_|, |overscroll_delta_x_|
-  // and |overscroll_delta_y_|).
-  void ProcessOverscroll(float delta_x,
+  // and |overscroll_delta_y_|). Returns true if overscroll was handled by the
+  // delegate.
+  bool ProcessOverscroll(float delta_x,
                          float delta_y,
                          blink::WebInputEvent::Type event_type);
 
   // Completes the desired action from the current gesture.
   void CompleteAction();
 
   // Sets the overscroll mode (and triggers callback in the delegate when
   // appropriate).
   void SetOverscrollMode(OverscrollMode new_mode);
 
@@ skipping 15 matching lines @@
   // The delegate that receives the overscroll updates. The delegate is not
   // owned by this controller.
   OverscrollControllerDelegate* delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(OverscrollController);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_OVERSCROLL_CONTROLLER_H_