Add always on top windows to the alt+tab list

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index c371f99d4c592bef00d79e37bc335ec93189bf3c..0ad9e24d5280b6257bd361787baf41b10124c720 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -253,6 +253,10 @@ class ASH_EXPORT Shell : ash::CursorDelegate {
   }
 #endif  // !defined(OS_MACOSX)
 
+  internal::ActivationController* activation_controller() {

[sky, 2012/08/02 21:18:00]

We shouldn't expose classes in the internal namespace here. It means anyone can
get a handle to them.

[Zachary Kuznia, 2012/08/06 05:56:03]

Done.

+    return activation_controller_.get();
+  }
+
   aura::shared::CompoundEventFilter* env_filter() {
     return env_filter_;
   }