feedback UI: use native window controls on Mac

chrome/browser/resources/feedback/js/topbar_handlers.js

Index: chrome/browser/resources/feedback/js/topbar_handlers.js
diff --git a/chrome/browser/resources/feedback/js/topbar_handlers.js b/chrome/browser/resources/feedback/js/topbar_handlers.js
index 793e0e5e16b1e4cc3a47a44338934d6fd1e93a2a..03e43e05c020416e9829cae06d011f14104f862c 100644
--- a/chrome/browser/resources/feedback/js/topbar_handlers.js
+++ b/chrome/browser/resources/feedback/js/topbar_handlers.js
@@ -6,6 +6,13 @@
  * Setup handlers for the minimize and close topbar buttons.
  */
 function initializeHandlers() {
+  // If this dialog is using system window controls, these elements aren't
+  // needed at all.
+  if (window.feedbackInfo.useSystemWindowFrame) {
+    $('minimize-button').hidden = true;
+    $('close-button').hidden = true;
+    return;
+  }
   $('minimize-button').addEventListener('click', function(e) {
     e.preventDefault();
     chrome.app.window.current().minimize();