input: Delay the dispatch of synthesized input event.

content/browser/renderer_host/input/synthetic_gesture_controller.cc

 // Copyright 2013 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.
 
 #include "content/browser/renderer_host/input/synthetic_gesture_controller.h"
 
 #include <utility>
 
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/trace_event/trace_event.h"
@@ skipping 21 matching lines @@
   bool was_empty = pending_gesture_queue_.IsEmpty();
 
   pending_gesture_queue_.Push(std::move(synthetic_gesture),
                               completion_callback);
 
   if (was_empty)
     StartGesture(*pending_gesture_queue_.FrontGesture());
 }
 
 void SyntheticGestureController::OnBeginFrame() {
-  // TODO(sad): Instead of dispatching the events immediately, dispatch after an
-  // offset.
-  DispatchNextEvent();
+  constexpr base::TimeDelta kSynthesizedDispatchDelay =
+      base::TimeDelta::FromMilliseconds(2);
+  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(

[dtapuska, 2017/05/17 16:30:45]

I don't think this is quite right. Didn't we want a repeating timer? that is
sync'd on the first main frame signal?

[sadrul, 2017/05/17 18:18:01]

Yep, that's where we want to go. I am trying to take smaller steps here (1)
dispatch at (begin-frame + offset) (2) dispatch at regular intervals after the
first (begin-frame + offset), still one event per begin-frame (3) dispatch more
than one events per begin-frame. This is step 1. I am happy to go to step 2 at
the same time if you don't think taking step 1 separately is necessary (although
I should probably leave a TODO explaining the next steps).

+      FROM_HERE,
+      base::BindOnce(
+          [](base::WeakPtr<SyntheticGestureController> weak_ptr) {
+            if (weak_ptr)
+              weak_ptr->DispatchNextEvent(base::TimeTicks::Now());
+          },
+          weak_ptr_factory_.GetWeakPtr()),
+      kSynthesizedDispatchDelay);
 }
 
 bool SyntheticGestureController::DispatchNextEvent(base::TimeTicks timestamp) {
   TRACE_EVENT0("input", "SyntheticGestureController::Flush");
   if (pending_gesture_queue_.IsEmpty())
     return false;
 
   SyntheticGesture::Result result =
       pending_gesture_queue_.FrontGesture()->ForwardInputEvents(
           timestamp, gesture_target_.get());
@@ skipping 36 matching lines @@
 }
 
 SyntheticGestureController::GestureAndCallbackQueue::GestureAndCallbackQueue() {
 }
 
 SyntheticGestureController::GestureAndCallbackQueue::
     ~GestureAndCallbackQueue() {
 }
 
 }  // namespace content