Introduce EventProcessor::OnEventProcessingStarted()

ui/aura/window_event_dispatcher.cc

 // Copyright 2014 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 "ui/aura/window_event_dispatcher.h"
 
 #include "base/bind.h"
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 417 matching lines @@
 void WindowEventDispatcher::ReleaseNativeCapture() {
   host_->ReleaseCapture();
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // WindowEventDispatcher, ui::EventProcessor implementation:
 ui::EventTarget* WindowEventDispatcher::GetRootTarget() {
   return window();
 }
 
-void WindowEventDispatcher::PrepareEventForDispatch(ui::Event* event) {
-  if (dispatching_held_event_) {
-    // The held events are already in |window()|'s coordinate system. So it is
-    // not necessary to apply the transform to convert from the host's
-    // coordinate system to |window()|'s coordinate system.
-    return;
-  }
-  if (event->IsLocatedEvent()) {
+bool WindowEventDispatcher::OnEventProcessingStarted(ui::Event* event) {
+  // The held events are already in |window()|'s coordinate system. So it is
+  // not necessary to apply the transform to convert from the host's
+  // coordinate system to |window()|'s coordinate system.
+  if (event->IsLocatedEvent() && !dispatching_held_event_)
     TransformEventForDeviceScaleFactor(static_cast<ui::LocatedEvent*>(event));
-  }
+
+  return true;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // WindowEventDispatcher, ui::EventDispatcherDelegate implementation:
 
 bool WindowEventDispatcher::CanDispatchToTarget(ui::EventTarget* target) {
   return event_dispatch_target_ == target;
 }
 
 ui::EventDispatchDetails WindowEventDispatcher::PreDispatchEvent(
@@ skipping 443 matching lines @@
 
     default:
       NOTREACHED();
       break;
   }
 
   PreDispatchLocatedEvent(target, event);
 }
 
 }  // namespace aura