Implement a callout widget for the active panel.

ash/wm/panel_layout_manager.h

Index: ash/wm/panel_layout_manager.h
diff --git a/ash/wm/panel_layout_manager.h b/ash/wm/panel_layout_manager.h
index 317cfbc48b956ce002a3b3a24785be28bb17e14d..e2de8125682cdd332f04461ccfe7d6d741f8f225 100644
--- a/ash/wm/panel_layout_manager.h
+++ b/ash/wm/panel_layout_manager.h
@@ -12,6 +12,7 @@
 #include "ash/launcher/launcher_icon_observer.h"
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
+#include "base/memory/scoped_ptr.h"
 #include "ui/aura/layout_manager.h"
 #include "ui/aura/window_observer.h"
 
@@ -23,6 +24,10 @@ namespace gfx {
 class Rect;
 }
 
+namespace views {
+class Widget;
+}
+
 namespace ash {
 class Launcher;
 
@@ -76,7 +81,9 @@ class ASH_EXPORT PanelLayoutManager : public aura::LayoutManager,
 
   // Called whenever the panel stacking order needs to be updated (e.g. focus
   // changes or a panel is moved).
-  void UpdateStacking(aura::Window* active_window);
+  void UpdateStacking(aura::Window* active_panel);
+
+  void UpdateCallout(aura::Window* active_panel);
 
   // Parent window associated with this layout manager.
   aura::Window* panel_container_;
@@ -91,6 +98,7 @@ class ASH_EXPORT PanelLayoutManager : public aura::LayoutManager,
   // The last active panel. Used to maintain stacking even if no panels are
   // currently focused.
   aura::Window* last_active_panel_;
+  scoped_ptr<views::Widget> callout_widget_;
 
   DISALLOW_COPY_AND_ASSIGN(PanelLayoutManager);
 };