Fix the comment of overlay_filter_ in Shell.

This should have been included in the CL below.
http://src.chromium.org/viewvc/chrome?view=rev&revision=148504

BUG=129834

Review URL: https://chromiumcodereview.appspot.com/10825081

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@149024 0039d316-1c4b-4281-b951-d872f2087c98

ash/shell.h

@@ -446,7 +446,7 @@ class ASH_EXPORT Shell : ash::CursorDelegate {
   scoped_ptr<internal::EventRewriterEventFilter> event_rewriter_filter_;
 
   // An event filter that pre-handles key events while the partial
-  // screenshot UI is active.
+  // screenshot UI or the keyboard overlay is active.
   scoped_ptr<internal::OverlayEventFilter> overlay_filter_;
 
   // An event filter which handles system level gestures