Refactor CopyNativeEvent and add events_mac.mm to start implementing stubs

ui/events/x/events_x.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 "ui/events/event_constants.h"
 
 #include <cmath>
 #include <string.h>
 #include <X11/extensions/XInput.h>
 #include <X11/extensions/XInput2.h>
@@ skipping 516 matching lines @@
       return gfx::Vector2d(0, -kWheelScrollAmount);
     case 6:
       return gfx::Vector2d(kWheelScrollAmount, 0);
     case 7:
       return gfx::Vector2d(-kWheelScrollAmount, 0);
     default:
       return gfx::Vector2d();
   }
 }
 
+base::NativeEvent CopyNativeEvent(const base::NativeEvent& event) {
+  if (!event || event->type == GenericEvent)
+    return NULL;
+  XEvent* copy = new XEvent;
+  *copy = *event;
+  return copy;
+}
+
+void ReleaseCopiedNativeEvent(const base::NativeEvent& event) { delete event; }
+
 void ClearTouchIdIfReleased(const base::NativeEvent& xev) {
   ui::EventType type = ui::EventTypeFromNative(xev);
   if (type == ui::ET_TOUCH_CANCELLED ||
       type == ui::ET_TOUCH_RELEASED) {
     ui::TouchFactory* factory = ui::TouchFactory::GetInstance();
     ui::DeviceDataManager* manager = ui::DeviceDataManager::GetInstance();
     double tracking_id;
     if (manager->GetEventData(
         *xev, ui::DeviceDataManager::DT_TOUCH_TRACKING_ID, &tracking_id)) {
       factory->ReleaseSlotForTrackingID(tracking_id);
@@ skipping 118 matching lines @@
   DeviceDataManager::GetInstance()->GetGestureTimes(
       native_event, start_time, end_time);
   return true;
 }
 
 bool IsTouchpadEvent(const base::NativeEvent& event) {
   return DeviceDataManager::GetInstance()->IsTouchpadXInputEvent(event);
 }
 
 }  // namespace ui