ash: Add comment about where to add new accelerators

ash/accelerators/accelerator_controller_delegate_aura.cc

 // Copyright 2016 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 "ash/accelerators/accelerator_controller_delegate_aura.h"
 
 #include <algorithm>
 #include <cmath>
 #include <string>
 #include <utility>
@@ skipping 343 matching lines @@
 
 AcceleratorControllerDelegateAura::~AcceleratorControllerDelegateAura() {}
 
 void AcceleratorControllerDelegateAura::SetScreenshotDelegate(
     std::unique_ptr<ScreenshotDelegate> screenshot_delegate) {
   screenshot_delegate_ = std::move(screenshot_delegate);
 }
 
 bool AcceleratorControllerDelegateAura::HandlesAction(
     AcceleratorAction action) {
+  // NOTE: When adding a new accelerator that only depends on //ash/common code,
+  // add it to accelerator_controller.cc instead. See class comment.
   switch (action) {
     case DEBUG_TOGGLE_DESKTOP_BACKGROUND_MODE:
     case DEBUG_TOGGLE_DEVICE_SCALE_FACTOR:
     case DEBUG_TOGGLE_ROOT_WINDOW_FULL_SCREEN:
     case DEBUG_TOGGLE_SHOW_DEBUG_BORDERS:
     case DEBUG_TOGGLE_SHOW_FPS_COUNTER:
     case DEBUG_TOGGLE_SHOW_PAINT_RECTS:
     case FOCUS_SHELF:
     case LAUNCH_APP_0:
     case LAUNCH_APP_1:
@@ skipping 270 matching lines @@
           message_center::NotifierId(
               message_center::NotifierId::SYSTEM_COMPONENT,
               system_notifier::kNotifierDeprecatedAccelerator),
           message_center::RichNotificationData(),
           new DeprecatedAcceleratorNotificationDelegate));
   message_center::MessageCenter::Get()->AddNotification(
       std::move(notification));
 }
 
 }  // namespace ash