Add flag to enable immersive fullscreen for v2 apps

ash/wm/caption_buttons/frame_maximize_button_observer.h

Index: ash/wm/caption_buttons/frame_maximize_button_observer.h
diff --git a/ash/wm/caption_buttons/frame_maximize_button_observer.h b/ash/wm/caption_buttons/frame_maximize_button_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..1962f60416cab585960d4b3b36dd66fc96f069d1
--- /dev/null
+++ b/ash/wm/caption_buttons/frame_maximize_button_observer.h
@@ -0,0 +1,26 @@
+// 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 ASH_WM_CAPTION_BUTTONS_FRAME_MAXIMIZE_BUTTON_OBSERVER_H_
+#define ASH_WM_CAPTION_BUTTONS_FRAME_MAXIMIZE_BUTTON_OBSERVER_H_
+
+#include "ash/ash_export.h"
+
+namespace views {
+class Widget;
+}
+
+namespace ash {
+
+class ASH_EXPORT FrameMaximizeButtonObserver {
+ public:
+  virtual ~FrameMaximizeButtonObserver() {}
+
+  // Called when the maximize button's help bubble is shown.
+  virtual void OnMaximizeBubbleShown(views::Widget* bubble) = 0;
+};
+
+}  // namespace ash
+
+#endif  // ASH_WM_CAPTION_BUTTONS_FRAME_MAXIMIZE_BUTTON_OBSERVER_H_