Allow component IME extension use app.window and add 'ime' window type for app window

ash/shell_window_ids.h

 // 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.
 
 #ifndef ASH_SHELL_WINDOW_IDS_H_
 #define ASH_SHELL_WINDOW_IDS_H_
 
 // Declarations of ids of special shell windows.
 
 namespace ash {
@@ skipping 55 matching lines @@
 
 // The container for the lock screen.
 const int kShellWindowId_LockScreenContainer = 15;
 
 // The container for the lock screen modal windows.
 const int kShellWindowId_LockSystemModalContainer = 16;
 
 // The container for the status area.
 const int kShellWindowId_StatusContainer = 17;
 
-// A parent container that holds the virtual keyboard container. This is to
-// ensure that the virtual keyboard is stacked above most containers but below
-// the mouse cursor, context menus and the power off animation.
-const int kShellWindowId_VirtualKeyboardParentContainer = 18;
+// A parent container that holds the virtual keyboard container and ime windows
+// if any. This is to ensure that the virtual keyboard or ime window is stacked
+// above most containers but below the mouse cursor and the power off animation.
+const int kShellWindowId_ImeWindowParentContainer = 18;
 
 // The container for menus.
 const int kShellWindowId_MenuContainer = 19;
 
 // The container for drag/drop images and tooltips.
 const int kShellWindowId_DragImageAndTooltipContainer = 20;
 
 // The container for bubbles briefly overlaid onscreen to show settings changes
 // (volume, brightness, input method bubbles, etc.).
 const int kShellWindowId_SettingBubbleContainer = 21;
 
 // The container for special components overlaid onscreen, such as the
 // region selector for partial screenshots.
 const int kShellWindowId_OverlayContainer = 22;
 
 // ID of the window created by PhantomWindowController or DragWindowController.
 const int kShellWindowId_PhantomWindow = 23;
 
 // The container for mouse cursor.
 const int kShellWindowId_MouseCursorContainer = 24;
 
 // The topmost container, used for power off animation.
 const int kShellWindowId_PowerButtonAnimationContainer = 25;
 
 }  // namespace ash
 
 
 #endif  // ASH_SHELL_WINDOW_IDS_H_