Allow MainThreadEventQueue to call the RenderWidget directly.

content/renderer/input/main_thread_event_queue.h

Index: content/renderer/input/main_thread_event_queue.h
diff --git a/content/renderer/input/main_thread_event_queue.h b/content/renderer/input/main_thread_event_queue.h
index 42edd0cfeaf5ee946f3baaaa70e26e9d685997e2..bc607903563030f0a8f5cd8963513ebdeb03a3af 100644
--- a/content/renderer/input/main_thread_event_queue.h
+++ b/content/renderer/input/main_thread_event_queue.h
@@ -7,6 +7,7 @@
 
 #include <deque>
 #include "base/feature_list.h"
+#include "base/memory/weak_ptr.h"
 #include "content/common/content_export.h"
 #include "content/common/input/input_event_ack_state.h"
 #include "content/common/input/input_event_dispatch_type.h"
@@ -20,23 +21,7 @@
 
 namespace content {
 
-class CONTENT_EXPORT MainThreadEventQueueClient {
- public:
-  // Handle an |event| that was previously queued (possibly
-  // coalesced with another event) to the |routing_id|'s
-  // channel. Implementors must implement this callback.
-  virtual void HandleEventOnMainThread(
-      int routing_id,
-      const blink::WebCoalescedInputEvent* event,
-      const ui::LatencyInfo& latency,
-      InputEventDispatchType dispatch_type) = 0;
-
-  virtual void SendInputEventAck(int routing_id,
-                                 blink::WebInputEvent::Type type,
-                                 InputEventAckState ack_result,
-                                 uint32_t touch_event_id) = 0;
-  virtual void NeedsMainFrame(int routing_id) = 0;
-};
+class RenderWidget;
 
 // MainThreadEventQueue implements a queue for events that need to be
 // queued between the compositor and main threads. This queue is managed
@@ -78,8 +63,6 @@ class CONTENT_EXPORT MainThreadEventQueue
     : public base::RefCountedThreadSafe<MainThreadEventQueue> {
  public:
   MainThreadEventQueue(
-      int routing_id,
-      MainThreadEventQueueClient* client,
       const scoped_refptr<base::SingleThreadTaskRunner>& main_task_runner,
       blink::scheduler::RendererScheduler* renderer_scheduler);
 
@@ -92,15 +75,22 @@ class CONTENT_EXPORT MainThreadEventQueue
   void DispatchRafAlignedInput(base::TimeTicks frame_time);
   void QueueClosure(const base::Closure& closure);
 
-  // Call once the main thread has handled an outstanding |type| event
-  // in flight.
-  void EventHandled(blink::WebInputEvent::Type type,
-                    blink::WebInputEventResult result,
-                    InputEventAckState ack_result);
+  void NotifySchedulerOfEventHandled(const blink::WebInputEvent& event,
+                                     InputEventAckState ack_result);
 
- private:
+  virtual InputEventAckState HandleEventOnMainThread(
+      const blink::WebCoalescedInputEvent& event,
+      const ui::LatencyInfo& latency,
+      InputEventDispatchType dispatch_type) = 0;
+
+  virtual void SendInputEventAck(blink::WebInputEvent::Type type,
+                                 InputEventAckState ack_result,
+                                 uint32_t touch_event_id) = 0;

[tdresser, 2017/04/10 15:54:17]

Why is SendInputEventAck separate from NotifySchedulerOfEventHandled?

[dtapuska, 2017/04/10 16:08:05]

Mainly for the tests. There is a mock renderer scheduler which doesn't create a
render widget. If you have a better idea I'm happy to hear it.

+  virtual void NeedsMainFrame() = 0;
+
+ protected:
   friend class base::RefCountedThreadSafe<MainThreadEventQueue>;
-  ~MainThreadEventQueue();
+  virtual ~MainThreadEventQueue();
   void QueueEvent(std::unique_ptr<MainThreadEventQueueTask> event);
   void PostTaskToMainThread();
   void DispatchEvents();
@@ -117,8 +107,6 @@ class CONTENT_EXPORT MainThreadEventQueue
 
   friend class MainThreadEventQueueTest;
   friend class MainThreadEventQueueInitializationTest;
-  int routing_id_;
-  MainThreadEventQueueClient* client_;
   std::unique_ptr<MainThreadEventQueueTask> in_flight_event_;
   bool last_touch_start_forced_nonblocking_due_to_fling_;
   bool enable_fling_passive_listener_flag_;
@@ -150,6 +138,31 @@ class CONTENT_EXPORT MainThreadEventQueue
   DISALLOW_COPY_AND_ASSIGN(MainThreadEventQueue);
 };
 
+class MainThreadEventQueueWithRenderWidget : public MainThreadEventQueue {

[tdresser, 2017/04/10 15:54:17]

Why doesn't the MainThreadEventQueue just have a weakptr to a RenderWidget?

[dtapuska, 2017/04/10 16:08:05]

I could do it that way but the abstraction is for tests. I don't believe there
is a MockRenderWidget

[tdresser, 2017/04/10 16:25:01]

Could we add a new interface which RenderWidget implements, which includes all
the functionality the MTEQ requires? Mocking that would be pretty easy.

[dtapuska, 2017/04/13 16:56:24]

Done.

+ public:
+  MainThreadEventQueueWithRenderWidget(
+      const base::WeakPtr<RenderWidget>& widget,
+      blink::scheduler::RendererScheduler* renderer_scheduler);
+
+  InputEventAckState HandleEventOnMainThread(
+      const blink::WebCoalescedInputEvent& event,
+      const ui::LatencyInfo& latency,
+      InputEventDispatchType dispatch_type) override;
+
+  void SendInputEventAck(blink::WebInputEvent::Type type,
+                         InputEventAckState ack_result,
+                         uint32_t touch_event_id) override;
+
+  void NeedsMainFrame() override;
+
+ private:
+  ~MainThreadEventQueueWithRenderWidget() override;
+
+  base::WeakPtr<RenderWidget> widget_;
+
+  DISALLOW_COPY_AND_ASSIGN(MainThreadEventQueueWithRenderWidget);
+};
+
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_INPUT_MAIN_THREAD_EVENT_QUEUE_H_