Merge pull request #4856 from Snuffleupagus/overlay-manager-keydown-preventDefault

[OverlayManager] Add preventDefault to the keydown event handler

web/overlay_manager.js

@@ -128,6 +128,7 @@ var OverlayManager = {
     var self = OverlayManager;
     if (self.active && evt.keyCode === 27) { // Esc key.
       self._closeThroughCaller();
+      evt.preventDefault();
     }
   },