Teach main thread event queue about closures.

content/renderer/input/input_event_filter.h

Index: content/renderer/input/input_event_filter.h
diff --git a/content/renderer/input/input_event_filter.h b/content/renderer/input/input_event_filter.h
index 939e723d25f5a18d5e6cb649c3691cba254aac63..b042751901871adceca0cf950eb81034cb0da65b 100644
--- a/content/renderer/input/input_event_filter.h
+++ b/content/renderer/input/input_event_filter.h
@@ -63,6 +63,12 @@ class CONTENT_EXPORT InputEventFilter : public InputHandlerManagerClient,
   void SetInputHandlerManager(InputHandlerManager*) override;
   void RegisterRoutingID(int routing_id) override;
   void UnregisterRoutingID(int routing_id) override;
+  void RegisterAssociatedRenderFrameRoutingID(
+      int render_frame_routing_id,
+      int render_view_routing_id) override;
+  void QueueClosureForMainThreadEventQueue(
+      int routing_id,
+      const base::Closure& closure) override;
   void DidOverscroll(int routing_id,
                      const ui::DidOverscrollParams& params) override;
   void DidStopFlinging(int routing_id) override;
@@ -102,7 +108,8 @@ class CONTENT_EXPORT InputEventFilter : public InputHandlerManagerClient,
  private:
   ~InputEventFilter() override;
 
-  void ForwardToHandler(const IPC::Message& message,
+  void ForwardToHandler(int routing_id,
+                        const IPC::Message& message,
                         base::TimeTicks received_time);
   void DidForwardToHandlerAndOverscroll(
       int routing_id,
@@ -129,13 +136,20 @@ class CONTENT_EXPORT InputEventFilter : public InputHandlerManagerClient,
   // Protects access to routes_.
   base::Lock routes_lock_;
 
-  // Indicates the routing_ids for which input events should be filtered.
+  // Indicates the routing ids for RenderViews for which input events
+  // should be filtered.
   std::set<int> routes_;
 
   using RouteQueueMap =
       std::unordered_map<int, scoped_refptr<MainThreadEventQueue>>;
+  // Maps RenderView routing ids to a MainThreadEventQueue.
   RouteQueueMap route_queues_;
 
+  using AssociatedRoutes = std::unordered_map<int, int>;
+  // Maps RenderFrame routing ids to RenderView routing ids so that
+  // events sent down the two routing pipes can be handled synchronously.
+  AssociatedRoutes associated_routes_;
+
   blink::scheduler::RendererScheduler* renderer_scheduler_;
 };