feedback UI: use native window controls on Mac

chrome/browser/resources/feedback/js/event_handler.js

 // Copyright 2013 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.
 
 <include src="data.js">
 
 /**
  * @type {number}
  * @const
  */
@@ skipping 242 matching lines @@
  * Callback which starts up the feedback UI.
  * @param {Object} feedbackInfo Object containing any initial feedback info.
  */
 function startFeedbackUI(feedbackInfo) {
   var win = chrome.app.window.get(FEEDBACK_DEFAULT_WINDOW_ID);
   if (win) {
     win.show();
     return;
   }
   chrome.app.window.create('html/default.html', {
-      frame: 'none',
+      frame: feedbackInfo.useSystemWindowFrame ? 'chrome' : 'none',
       id: FEEDBACK_DEFAULT_WINDOW_ID,
       width: FEEDBACK_WIDTH,
       height: FEEDBACK_HEIGHT,
       hidden: true,
       resizable: false },
       function(appWindow) {
         var request = new FeedbackRequest(feedbackInfo);
 
         // The feedbackInfo member of the new window should refer to the one in
         // its corresponding FeedbackRequest object to avoid copying and
@@ skipping 16 matching lines @@
         // Observe when the window is closed.
         appWindow.onClosed.addListener(function() {
           request.onWindowClosed();
         });
       });
 }
 
 chrome.runtime.onMessage.addListener(feedbackReadyHandler);
 chrome.runtime.onMessageExternal.addListener(requestFeedbackHandler);
 chrome.feedbackPrivate.onFeedbackRequested.addListener(startFeedbackUI);