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

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

Index: chrome/browser/resources/settings/site_settings/add_site_dialog.js
diff --git a/chrome/browser/resources/settings/site_settings/add_site_dialog.js b/chrome/browser/resources/settings/site_settings/add_site_dialog.js
index c61483a265f72d542e9ec7ab94d7fe59b46931f1..1750483931e170734e668d7cad097b03e6fe0589 100644
--- a/chrome/browser/resources/settings/site_settings/add_site_dialog.js
+++ b/chrome/browser/resources/settings/site_settings/add_site_dialog.js
@@ -43,12 +43,12 @@ Polymer({
 
   /** Open the dialog. */
   open: function() {
-    this.addWebUIListener('onIncognitoStatusChanged', function(hasIncognito) {
+    this.addWebUIListener('onIncognitoStatusChanged', hasIncognito => {
       this.$.incognito.checked = false;
       this.showIncognitoSessionOnly_ = hasIncognito &&
           !loadTimeData.getBoolean('isGuest') &&
           this.contentSetting != settings.ContentSetting.SESSION_ONLY;
-    }.bind(this));
+    });
     this.browserProxy.updateIncognitoStatus();
     this.$.dialog.showModal();
   },
@@ -66,10 +66,10 @@ Polymer({
       return;
     }
 
-    this.browserProxy.isPatternValid(this.site_).then(function(isValid) {
+    this.browserProxy.isPatternValid(this.site_).then(isValid => {
       this.$.site.invalid = !isValid;
       this.$.add.disabled = !isValid;
-    }.bind(this));
+    });
   },
 
   /** @private */