Leave fullscreen mode in an app window when ESC key is pressed.

apps/shell_window.h

 // Copyright 2013 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.
 
 #ifndef APPS_SHELL_WINDOW_H_
 #define APPS_SHELL_WINDOW_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "chrome/browser/extensions/extension_icon_image.h"
@@ skipping 330 matching lines @@
       const content::MediaResponseCallback& callback) OVERRIDE;
   virtual content::WebContents* OpenURLFromTab(
       content::WebContents* source,
       const content::OpenURLParams& params) OVERRIDE;
   virtual void AddNewContents(content::WebContents* source,
                               content::WebContents* new_contents,
                               WindowOpenDisposition disposition,
                               const gfx::Rect& initial_pos,
                               bool user_gesture,
                               bool* was_blocked) OVERRIDE;
+  virtual bool PreHandleKeyboardEvent(
+      content::WebContents* source,
+      const content::NativeWebKeyboardEvent& event,
+      bool* is_keyboard_shortcut) OVERRIDE;
   virtual void HandleKeyboardEvent(
       content::WebContents* source,
       const content::NativeWebKeyboardEvent& event) OVERRIDE;
   virtual void RequestToLockMouse(content::WebContents* web_contents,
                                   bool user_gesture,
                                   bool last_unlocked_by_target) OVERRIDE;
 
   // content::WebContentsObserver implementation.
   virtual void DidFirstVisuallyNonEmptyPaint(int32 page_id) OVERRIDE;
 
@@ skipping 100 matching lines @@
 
   // Whether the delayed Show() call was for an active or inactive window.
   ShowType delayed_show_type_;
 
   DISALLOW_COPY_AND_ASSIGN(ShellWindow);
 };
 
 }  // namespace apps
 
 #endif  // APPS_SHELL_WINDOW_H_