feedback UI: use native window controls on Mac

chrome/browser/extensions/api/feedback_private/feedback_private_api.cc

 // 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 "chrome/browser/extensions/api/feedback_private/feedback_private_api.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/lazy_instance.h"
@@ skipping 112 matching lines @@
     FeedbackInfo info;
     info.description = description_template;
     info.category_tag = base::MakeUnique<std::string>(category_tag);
     info.page_url = base::MakeUnique<std::string>(page_url.spec());
     info.system_information.reset(new SystemInformationList);
     // The manager is only available if tracing is enabled.
     if (TracingManager* manager = TracingManager::Get()) {
       info.trace_id.reset(new int(manager->RequestTrace()));
     }
     info.flow = flow;
+#if defined(OS_MACOSX)
+    info.use_system_window_frame = true;
+#else
+    info.use_system_window_frame = false;
+#endif
 
     std::unique_ptr<base::ListValue> args =
         feedback_private::OnFeedbackRequested::Create(info);
 
     std::unique_ptr<Event> event(new Event(
         events::FEEDBACK_PRIVATE_ON_FEEDBACK_REQUESTED,
         feedback_private::OnFeedbackRequested::kEventName, std::move(args)));
     event->restrict_to_browser_context = browser_context_;
 
     EventRouter::Get(browser_context_)
@@ skipping 190 matching lines @@
       content::RecordAction(
           base::UserMetricsAction("Feedback.SrtPromptClosed"));
       break;
     default:
       return RespondNow(Error("Invalid arugment."));
   }
   return RespondNow(NoArguments());
 }
 
 }  // namespace extensions