Make tapDown async.

content/browser/renderer_host/overscroll_controller.cc

 // Copyright (c) 2012 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/overscroll_controller.h"
 
+#include "content/browser/renderer_host/input/gesture_event_filter.h"
 #include "content/browser/renderer_host/overscroll_controller_delegate.h"
 #include "content/browser/renderer_host/render_widget_host_impl.h"
 #include "content/public/browser/overscroll_configuration.h"
 #include "content/public/browser/render_widget_host_view.h"
 
 using WebKit::WebInputEvent;
 
 namespace content {
 
 OverscrollController::OverscrollController(
@@ skipping 80 matching lines @@
     // Consume the event only if it updates the overscroll state.
     if (ProcessEventForOverscroll(event))
       return false;
   }
 
   return true;
 }
 
 void OverscrollController::ReceivedEventACK(const WebKit::WebInputEvent& event,
                                             bool processed) {
+  if (GestureEventFilter::IsGestureEventTypeAsync(event.type))

[jdduke (slow), 2013/09/30 15:42:56]

Make this a DCHECK(!GestureEventFilter::IsGestureEventTypeAsync(event.type)); if
the ack has made it to the OverscrollController, we have a problem.

[tdresser, 2013/09/30 18:05:03]

Done.

+    return;
   if (processed) {
     // If a scroll event is consumed by the page, i.e. some content on the page
     // has been scrolled, then there is not going to be an overscroll gesture,
     // until the current scroll ends, and a new scroll gesture starts.
     if (scroll_state_ == STATE_UNKNOWN &&
         (event.type == WebKit::WebInputEvent::MouseWheel ||
          event.type == WebKit::WebInputEvent::GestureScrollUpdate)) {
       scroll_state_ = STATE_CONTENT_SCROLLING;
     }
     return;
@@ skipping 245 matching lines @@
   overscroll_mode_ = mode;
   if (overscroll_mode_ == OVERSCROLL_NONE)
     overscroll_delta_x_ = overscroll_delta_y_ = 0.f;
   else
     scroll_state_ = STATE_OVERSCROLLING;
   if (delegate_)
     delegate_->OnOverscrollModeChange(old_mode, overscroll_mode_);
 }
 
 }  // namespace content