Refactor CopyNativeEvent and add events_mac.mm to start implementing stubs

ui/events/cocoa/cocoa_event_utils.mm

 // 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.
 
 #import "ui/events/cocoa/cocoa_event_utils.h"
 
 #include "ui/events/event_constants.h"
 #include "ui/events/event_utils.h"
 
 namespace {
@@ skipping 16 matching lines @@
 
   NSEventType type = [event type];
   return type == NSOtherMouseDown || type == NSOtherMouseDragged ||
          type == NSOtherMouseUp;
 }
 
 }  // namespace
 
 namespace ui {
 
-int EventFlagsFromNative(const base::NativeEvent& event) {
-  NSUInteger modifiers = [event modifierFlags];
-  return EventFlagsFromNSEventWithModifiers(event, modifiers);
-}
-
 int EventFlagsFromModifiers(NSUInteger modifiers) {
   int flags = 0;
   flags |= (modifiers & NSAlphaShiftKeyMask) ? ui::EF_CAPS_LOCK_DOWN : 0;
   flags |= (modifiers & NSShiftKeyMask) ? ui::EF_SHIFT_DOWN : 0;
   flags |= (modifiers & NSControlKeyMask) ? ui::EF_CONTROL_DOWN : 0;
   flags |= (modifiers & NSAlternateKeyMask) ? ui::EF_ALT_DOWN : 0;
   flags |= (modifiers & NSCommandKeyMask) ? ui::EF_COMMAND_DOWN : 0;
   return flags;
 }
 
 int EventFlagsFromNSEventWithModifiers(NSEvent* event, NSUInteger modifiers) {
   int flags = EventFlagsFromModifiers(modifiers);
   flags |= IsLeftButtonEvent(event) ? ui::EF_LEFT_MOUSE_BUTTON : 0;
   flags |= IsRightButtonEvent(event) ? ui::EF_RIGHT_MOUSE_BUTTON : 0;
   flags |= IsMiddleButtonEvent(event) ? ui::EF_MIDDLE_MOUSE_BUTTON : 0;
   return flags;
 }
 
 }  // namespace ui