app_shell: Remove some NOTIMPLEMENTED from ShellNativeAppWindow

extensions/shell/browser/shell_app_window_client.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 "extensions/shell/browser/shell_app_window_client.h"
 
+#include <vector>
+
 #include "extensions/browser/app_window/app_window.h"
 #include "extensions/shell/browser/desktop_controller.h"
 #include "extensions/shell/browser/shell_native_app_window.h"
 
 namespace extensions {
 
 ShellAppWindowClient::ShellAppWindowClient() {
 }
 
 ShellAppWindowClient::~ShellAppWindowClient() {
@@ skipping 15 matching lines @@
       AppWindow* window,
       const AppWindow::CreateParams& params) {
   ShellNativeAppWindow* native_app_window =
       new ShellNativeAppWindow(window, params);
   DesktopController::instance()->AddAppWindow(
       native_app_window->GetNativeWindow());
   return native_app_window;
 }
 
 void ShellAppWindowClient::IncrementKeepAliveCount() {
-  NOTIMPLEMENTED();
+  // app_shell runs until the system powers off, so it doesn't need to track
+  // open apps or windows to keep itself alive.
 }
 
 void ShellAppWindowClient::DecrementKeepAliveCount() {
-  NOTIMPLEMENTED();
+  // See IncrementKeepAliveCount().
 }
 
 void ShellAppWindowClient::OpenDevToolsWindow(
     content::WebContents* web_contents,
     const base::Closure& callback) {
   NOTIMPLEMENTED();
 }
 
 bool ShellAppWindowClient::IsCurrentChannelOlderThanDev() {
   return false;
 }
 
 }  // namespace extensions