MD Settings: Convert all usages of .bind(this) to use ES6 arrow function.

chrome/browser/resources/settings/site_settings/edit_exception_dialog.js

 // Copyright 2017 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-edit-exception-dialog' is a component for editing a
  * site exception entry.
  */
 Polymer({
   is: 'settings-edit-exception-dialog',
@@ skipping 50 matching lines @@
     this.$.dialog.close();
   },
 
   /** @private */
   validate_: function() {
     if (this.$$('paper-input').value.trim() == '') {
       this.invalid_ = true;
       return;
     }
 
-    this.browserProxy_.isPatternValid(this.origin_).then(function(isValid) {
+    this.browserProxy_.isPatternValid(this.origin_).then(isValid => {
       this.invalid_ = !isValid;
-    }.bind(this));
+    });
   },
 });