[POC; Not for Review] Don't use PostTask queueing between compositor and main thread.

content/renderer/input/main_thread_event_queue.cc

Index: content/renderer/input/main_thread_event_queue.cc
diff --git a/content/renderer/input/main_thread_event_queue.cc b/content/renderer/input/main_thread_event_queue.cc
index 243bc4fe9508b0386899b6c22929c0e8ebfda206..b40555967c9b71d82dd145c01915e3689d52d775 100644
--- a/content/renderer/input/main_thread_event_queue.cc
+++ b/content/renderer/input/main_thread_event_queue.cc
@@ -3,12 +3,20 @@
 // found in the LICENSE file.
 
 #include "content/renderer/input/main_thread_event_queue.h"
+#include "content/common/input_messages.h"
 
 namespace content {
 
-MainThreadEventQueue::MainThreadEventQueue(int routing_id,
-                                           MainThreadEventQueueClient* client)
-    : routing_id_(routing_id), client_(client), is_flinging_(false) {}
+MainThreadEventQueue::MainThreadEventQueue(
+    int routing_id,
+    MainThreadEventQueueClient* client,
+    const base::Callback<void(const IPC::Message&)>& main_listener,
+    const scoped_refptr<base::SingleThreadTaskRunner>& main_task_runner)
+    : routing_id_(routing_id),
+      client_(client),
+      is_flinging_(false),
+      main_task_runner_(main_task_runner),
+      main_listener_(main_listener) {}
 
 MainThreadEventQueue::~MainThreadEventQueue() {}
 
@@ -41,24 +49,7 @@ bool MainThreadEventQueue::HandleEvent(
       modified_dispatch_type_event.event.dispatchType =
           blink::WebInputEvent::ListenersNonBlockingPassive;
     }
-
-    if (wheel_events_.state() == WebInputEventQueueState::ITEM_PENDING) {
-      wheel_events_.Queue(modified_dispatch_type_event);
-    } else {
-      if (non_blocking) {
-        wheel_events_.set_state(WebInputEventQueueState::ITEM_PENDING);
-        client_->SendEventToMainThread(routing_id_,
-                                       &modified_dispatch_type_event.event,
-                                       latency, dispatch_type);
-      } else {
-        // If there is nothing in the event queue and the event is
-        // blocking pass the |original_dispatch_type| to avoid
-        // having the main thread call us back as an optimization.
-        client_->SendEventToMainThread(routing_id_,
-                                       &modified_dispatch_type_event.event,
-                                       latency, original_dispatch_type);
-      }
-    }
+    QueueWheelEvent(modified_dispatch_type_event);
   } else if (blink::WebInputEvent::isTouchEventType(event->type)) {
     PendingTouchEvent modified_dispatch_type_event =
         PendingTouchEvent(*static_cast<const blink::WebTouchEvent*>(event),
@@ -72,52 +63,150 @@ bool MainThreadEventQueue::HandleEvent(
           blink::WebInputEvent::ListenersNonBlockingPassive;
     }
 
-    if (touch_events_.state() == WebInputEventQueueState::ITEM_PENDING) {
-      touch_events_.Queue(modified_dispatch_type_event);
-    } else {
-      if (non_blocking) {
-        touch_events_.set_state(WebInputEventQueueState::ITEM_PENDING);
-        client_->SendEventToMainThread(routing_id_,
-                                       &modified_dispatch_type_event.event,
-                                       latency, dispatch_type);
-      } else {
-        // If there is nothing in the event queue and the event is
-        // blocking pass the |original_dispatch_type| to avoid
-        // having the main thread call us back as an optimization.
-        client_->SendEventToMainThread(routing_id_,
-                                       &modified_dispatch_type_event.event,
-                                       latency, original_dispatch_type);
-      }
-    }
+    QueueTouchEvent(modified_dispatch_type_event);
+  } else if (blink::WebInputEvent::isMouseEventType(event->type)) {
+    PendingMouseEvent modified_dispatch_type_event =
+        PendingMouseEvent(*static_cast<const blink::WebMouseEvent*>(event),
+                          latency, dispatch_type);
+    QueueMouseEvent(modified_dispatch_type_event);
   } else {
-    client_->SendEventToMainThread(routing_id_, event, latency,
-                                   original_dispatch_type);
+    SendEventToMainThread(event, latency, original_dispatch_type);
   }
 
   // send an ack when we are non-blocking.
   return non_blocking;
 }
 
-void MainThreadEventQueue::EventHandled(blink::WebInputEvent::Type type) {
-  if (type == blink::WebInputEvent::MouseWheel) {
-    if (!wheel_events_.empty()) {
-      std::unique_ptr<PendingMouseWheelEvent> event = wheel_events_.Pop();
-      client_->SendEventToMainThread(routing_id_, &event->event, event->latency,
+void MainThreadEventQueue::EventHandled(blink::WebInputEvent::Type type) {}

[tdresser, 2016/05/30 14:05:32]

So we'd get rid of this completely?

[dtapuska, 2016/06/01 18:22:53]

Yes

+
+void MainThreadEventQueue::SendEventToMainThread(
+    const blink::WebInputEvent* event,
+    const ui::LatencyInfo& latency,
+    InputEventDispatchType dispatch_type) {
+  IPC::Message new_msg =
+      InputMsg_HandleInputEvent(routing_id_, event, latency, dispatch_type);
+
+  main_task_runner_->PostTask(FROM_HERE, base::Bind(main_listener_, new_msg));
+}
+
+void MainThreadEventQueue::PopWheelEventOnMainThread() {
+  std::unique_ptr<PendingMouseWheelEvent> event;
+  {
+    base::AutoLock lock(event_queue_mutex_);
+    if (!wheel_events_.empty())

[tdresser, 2016/05/30 14:05:32]

Should this case ever occur?

[dtapuska, 2016/06/01 18:22:54]

No it shouldn't can add dcheck

+      event = wheel_events_.Pop();
+  }
+
+  if (event) {

[tdresser, 2016/05/30 14:05:32]

Should this ever not be true?

[dtapuska, 2016/06/01 18:22:53]

No it shouldn't

+    client_->HandleEventOnMainThread(routing_id_, &event->event, event->latency,
                                      event->type);
-    } else {
-      wheel_events_.set_state(WebInputEventQueueState::ITEM_NOT_PENDING);
+  }
+
+  {
+    base::AutoLock lock(event_queue_mutex_);
+    if (!wheel_events_.empty()) {
+      SendWheelEventNotificationToMainThread();
     }
-  } else if (blink::WebInputEvent::isTouchEventType(type)) {
+  }
+}
+
+void MainThreadEventQueue::PopTouchEventOnMainThread() {
+  std::unique_ptr<PendingTouchEvent> event;
+  size_t size;
+  {
+    base::AutoLock lock(event_queue_mutex_);
+    if (!touch_events_.empty())
+      event = touch_events_.Pop();
+    size = touch_events_.size();
+  }
+
+  LOG(ERROR) << size;
+  if (event) {
+    client_->HandleEventOnMainThread(routing_id_, &event->event, event->latency,
+                                     event->type);
+  }
+
+  {
+    base::AutoLock lock(event_queue_mutex_);
     if (!touch_events_.empty()) {
-      std::unique_ptr<PendingTouchEvent> event = touch_events_.Pop();
-      client_->SendEventToMainThread(routing_id_, &event->event, event->latency,
+      SendTouchEventNotificationToMainThread();
+    }
+  }
+}
+
+void MainThreadEventQueue::PopMouseEventOnMainThread() {
+  std::unique_ptr<PendingMouseEvent> event;
+  size_t size;
+  {
+    base::AutoLock lock(event_queue_mutex_);
+    if (!mouse_events_.empty())
+      event = mouse_events_.Pop();
+    size = mouse_events_.size();
+  }
+
+  if (event) {
+    client_->HandleEventOnMainThread(routing_id_, &event->event, event->latency,
                                      event->type);
-    } else {
-      touch_events_.set_state(WebInputEventQueueState::ITEM_NOT_PENDING);
+  }
+
+  {
+    base::AutoLock lock(event_queue_mutex_);
+    if (!mouse_events_.empty()) {
+      SendMouseEventNotificationToMainThread();
     }
-  } else {
-    NOTREACHED() << "Invalid passive event type";
   }
 }
 
+void MainThreadEventQueue::SendWheelEventNotificationToMainThread() {
+  main_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&MainThreadEventQueue::PopWheelEventOnMainThread,
+                            base::Unretained(this)));
+}
+
+void MainThreadEventQueue::SendTouchEventNotificationToMainThread() {
+  main_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&MainThreadEventQueue::PopTouchEventOnMainThread,
+                            base::Unretained(this)));
+}
+
+void MainThreadEventQueue::SendMouseEventNotificationToMainThread() {
+  main_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&MainThreadEventQueue::PopMouseEventOnMainThread,
+                            base::Unretained(this)));
+}
+
+void MainThreadEventQueue::QueueWheelEvent(
+    const PendingMouseWheelEvent& event) {
+  size_t pending;
+  {
+    base::AutoLock lock(event_queue_mutex_);
+    pending = wheel_events_.size();
+    wheel_events_.Queue(event);
+  }
+  if (pending == 0)
+    SendWheelEventNotificationToMainThread();
+}
+
+void MainThreadEventQueue::QueueTouchEvent(const PendingTouchEvent& event) {
+  size_t pending;
+  {
+    base::AutoLock lock(event_queue_mutex_);
+    pending = touch_events_.size();
+    touch_events_.Queue(event);
+  }
+  if (pending == 0)
+    SendTouchEventNotificationToMainThread();
+}
+
+void MainThreadEventQueue::QueueMouseEvent(const PendingMouseEvent& event) {
+  size_t pending;
+  {
+    base::AutoLock lock(event_queue_mutex_);
+    pending = mouse_events_.size();
+    mouse_events_.Queue(event);
+  }
+  if (pending == 0)
+    SendMouseEventNotificationToMainThread();
+}
+
 }  // namespace content