Allow MainThreadEventQueue to call the RenderWidget directly.

content/renderer/input/main_thread_event_queue.h

 // Copyright 2016 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_RENDERER_INPUT_MAIN_THREAD_EVENT_QUEUE_H_
 #define CONTENT_RENDERER_INPUT_MAIN_THREAD_EVENT_QUEUE_H_
 
 #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"
 #include "content/public/common/content_features.h"
 #include "content/renderer/input/main_thread_event_queue_task_list.h"
 #include "content/renderer/input/scoped_web_input_event_with_latency_info.h"
 #include "third_party/WebKit/public/platform/WebInputEvent.h"
 #include "third_party/WebKit/public/platform/scheduler/renderer/renderer_scheduler.h"
 #include "ui/events/blink/web_input_event_traits.h"
 #include "ui/latency/latency_info.h"
 
 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
 // by a lock where events are enqueued by the compositor thread
 // and dequeued by the main thread.
 //
 // Below some example flows are how the code behaves.
 // Legend: B=Browser, C=Compositor, M=Main Thread, NB=Non-blocking
 //         BL=Blocking, PT=Post Task, ACK=Acknowledgement
 //
@@ skipping 21 matching lines @@
 //         (queue)
 //            ---(PT)-->
 //                  (deque)
 //                  (deque)
 //   <-------(ACK)------
 //
 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);
 
   // Called once the compositor has handled |event| and indicated that it is
   // a non-blocking event to be queued to the main thread.
   bool HandleEvent(ui::WebScopedInputEvent event,
                    const ui::LatencyInfo& latency,
                    InputEventDispatchType dispatch_type,
                    InputEventAckState ack_result);
   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();
   void DispatchInFlightEvent();
   void PossiblyScheduleMainFrame();
 
   void SendEventToMainThread(const blink::WebInputEvent* event,
                              const ui::LatencyInfo& latency,
                              InputEventDispatchType original_dispatch_type);
 
   bool IsRafAlignedInputDisabled() const;
   bool IsRafAlignedEvent(
       const std::unique_ptr<MainThreadEventQueueTask>& item) const;
 
   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_;
   bool enable_non_blocking_due_to_main_thread_responsiveness_flag_;
   base::TimeDelta main_thread_responsiveness_threshold_;
   bool handle_raf_aligned_touch_input_;
   bool handle_raf_aligned_mouse_input_;
 
   // Contains data to be shared between main thread and compositor thread.
   struct SharedState {
@@ skipping 11 matching lines @@
   // Lock used to serialize |shared_state_|.
   base::Lock shared_state_lock_;
   SharedState shared_state_;
 
   scoped_refptr<base::SingleThreadTaskRunner> main_task_runner_;
   blink::scheduler::RendererScheduler* renderer_scheduler_;
 
   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_