Make mouse wheel events trigger WebContentsObserver::DidGetUserInteraction.

content/browser/renderer_host/render_widget_host_impl.h

Index: content/browser/renderer_host/render_widget_host_impl.h
diff --git a/content/browser/renderer_host/render_widget_host_impl.h b/content/browser/renderer_host/render_widget_host_impl.h
index ccfeeb98794ad261064dd648c3f6c20d6983c276..ef80f9e9a9a69ba3dc15a50d2d36601630e02991 100644
--- a/content/browser/renderer_host/render_widget_host_impl.h
+++ b/content/browser/renderer_host/render_widget_host_impl.h
@@ -18,7 +18,7 @@
 #include "base/process/kill.h"
 #include "base/strings/string16.h"
 #include "base/time/time.h"
-#include "base/timer/timer.h"
+#include "base/timer/elapsed_timer.h"
 #include "build/build_config.h"
 #include "cc/resources/shared_bitmap.h"
 #include "content/browser/renderer_host/event_with_latency_info.h"
@@ -853,6 +853,11 @@ class CONTENT_EXPORT RenderWidgetHostImpl : public RenderWidgetHost,
   // renderer process before clearing any previously displayed content.
   base::TimeDelta new_content_rendering_delay_;
 
+  // Timer used to batch together mouse wheel events for the delegate
+  // OnUserInteraction method. A wheel event is only dispatched when a wheel
+  // event has not been seen for kMouseWheelCoalesceInterval seconds prior.
+  scoped_ptr<base::ElapsedTimer> mouse_wheel_coalesce_timer_;
+
   base::WeakPtrFactory<RenderWidgetHostImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostImpl);