Notify OverscrollController of gesture events in plugins.

content/browser/renderer_host/render_widget_host_view_base.h

Index: content/browser/renderer_host/render_widget_host_view_base.h
diff --git a/content/browser/renderer_host/render_widget_host_view_base.h b/content/browser/renderer_host/render_widget_host_view_base.h
index 3f0cdab0dfba80e3771da2b36eb19db1fb1e54f6..d4027aab26c5ce34ef34ae15f6f65aff41d631a4 100644
--- a/content/browser/renderer_host/render_widget_host_view_base.h
+++ b/content/browser/renderer_host/render_widget_host_view_base.h
@@ -188,6 +188,10 @@ class CONTENT_EXPORT RenderWidgetHostViewBase : public RenderWidgetHostView,
   virtual InputEventAckState FilterInputEvent(
       const blink::WebInputEvent& input_event);
 
+  // Allows a root RWHV to filter gesture events in a child.
+  virtual InputEventAckState FilterChildGestureEvent(
+      const blink::WebGestureEvent& gesture_event);
+
   // Called by the host when it requires an input flush; the flush call should
   // by synchronized with BeginFrame.
   virtual void OnSetNeedsFlushInput();