MD Settings: Update some dialogs to accept Enter key.

chrome/browser/resources/settings/search_engines_page/search_engine_dialog.js

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @fileoverview 'settings-search-engine-dialog' is a component for adding
  * or editing a search engine entry.
  */
 Polymer({
   is: 'settings-search-engine-dialog',
@@ skipping 68 matching lines @@
     this.$.dialog.showModal();
   },
 
   /** @private */
   cancel_: function() {
     this.$.dialog.cancel();
   },
 
   /** @private */
   onActionButtonTap_: function() {
+    // This method may be called via keybinding, so we ignore invalid input.
+    if (this.$.actionButton.disabled)
+      return;
+
     this.browserProxy_.searchEngineEditCompleted(
         this.searchEngine_, this.keyword_, this.queryUrl_);
     this.$.dialog.close();
   },
 
   /**
    * @param {!Event} event
    * @private
    */
   validate_: function(event) {
@@ skipping 17 matching lines @@
   /** @private */
   updateActionButtonState_: function() {
     var allValid = [
       this.$.searchEngine, this.$.keyword, this.$.queryUrl
     ].every(function(inputElement) {
       return !inputElement.invalid && inputElement.value.length > 0;
     });
     this.$.actionButton.disabled = !allValid;
   },
 });