Make mouse wheel events trigger WebContentsObserver::DidGetUserInteraction.

content/browser/renderer_host/render_widget_host_delegate.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_RENDER_WIDGET_HOST_DELEGATE_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_DELEGATE_H_
 
 #include "base/basictypes.h"
 #include "build/build_config.h"
 #include "content/common/content_export.h"
@@ skipping 47 matching lines @@
   // Callback to inform the browser that the renderer did not process the
   // specified events. This gives an opportunity to the browser to process the
   // event (used for keyboard shortcuts).
   virtual void HandleKeyboardEvent(const NativeWebKeyboardEvent& event) {}
 
   // Callback to inform the browser that the renderer did not process the
   // specified mouse wheel event.  Returns true if the browser has handled
   // the event itself.
   virtual bool HandleWheelEvent(const blink::WebMouseWheelEvent& event);
 
-  // Notification the user has performed a direct interaction (mouse down, raw
-  // key down, or gesture tap) while focus was on the page. This is used to
-  // inform the delegate that a user is interacting with a site.
+  // Notification the user has performed a direct interaction (mouse down, mouse
+  // wheel, raw key down, or gesture tap) while focus was on the page. Informs
+  // the delegate that a user is interacting with a site. Only the first mouse
+  // wheel event during a scroll will trigger this method.
   virtual void OnUserInteraction(const blink::WebInputEvent::Type type) {}
 
   // Callback to give the browser a chance to handle the specified gesture
   // event before sending it to the renderer.
   // Returns true if the |event| was handled.
   virtual bool PreHandleGestureEvent(const blink::WebGestureEvent& event);
 
   // Notifies that screen rects were sent to renderer process.
   virtual void DidSendScreenRects(RenderWidgetHostImpl* rwh) {}
 
@@ skipping 28 matching lines @@
   virtual gfx::NativeViewAccessible GetParentNativeViewAccessible();
 #endif
 
  protected:
   virtual ~RenderWidgetHostDelegate() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_DELEGATE_H_