MD Settings: Search engines page, open "manage extension" in new tab.

chrome/browser/resources/settings/search_engines_page/search_engines_browser_proxy.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 A helper object used from the "Manage search engines" section
  * to interact with the browser.
  */
 
 /**
@@ skipping 113 matching lines @@
           'validateSearchEngineInput', fieldName, fieldValue);
     },
 
     /** @override */
     disableExtension: function(extensionId) {
       chrome.send('disableExtension', [extensionId]);
     },
 
     /** @override */
     manageExtension: function(extensionId) {
-      window.location = 'chrome://extensions?id=' + extensionId;
+      window.open('chrome://extensions?id=' + extensionId);
     },
   };
 
   return {
     SearchEnginesBrowserProxy: SearchEnginesBrowserProxy,
     SearchEnginesBrowserProxyImpl: SearchEnginesBrowserProxyImpl,
   };
 });