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

ash/shell_window_ids.h

Index: ash/shell_window_ids.h
diff --git a/ash/shell_window_ids.h b/ash/shell_window_ids.h
index f01e74b3715b26eb78026c7da16ca4a8355a2b94..4e3f49dc770401face3122429945232cb1751988 100644
--- a/ash/shell_window_ids.h
+++ b/ash/shell_window_ids.h
@@ -90,10 +90,10 @@ const int kShellWindowId_OverlayContainer = 21;
 // ID of the window created by PhantomWindowController or DragWindowController.
 const int kShellWindowId_PhantomWindow = 22;
 
-// 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 and the power off animation.
-const int kShellWindowId_VirtualKeyboardParentContainer = 23;
+// 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 = 23;
 
 // The container for mouse cursor.
 const int kShellWindowId_MouseCursorContainer = 24;