[MD Settings][People] Profile Avatar Selector won't lose focus on pressing esc

BUG=653836
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2428083002
Cr-Commit-Position: refs/heads/master@{#427195}

ui/webui/resources/cr_elements/cr_profile_avatar_selector/cr_profile_avatar_selector_grid.js

@@ -34,6 +34,15 @@ Polymer({
     event.detail.keyboardEvent.preventDefault();
   },
 
+  /**
+   * Handler that is called when the esc key is pressed.
+   * @param {CustomEvent} event A key combination event.
+   * @private
+   */
+  _onEscKey: function(event) {
+    // Override the original behavior by doing nothing.
+  },
+
   /**
    * Focuses an item on the same column as the currently focused item and on a
    * row below or above the focus row by the given offset. Focus wraps if