Mac Support for drag-and-drop tests that start dragging via mouse simulation.

content/public/test/browser_test_utils.cc

 // Copyright (c) 2012 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 "content/public/test/browser_test_utils.h"
 
 #include <stddef.h>
 #include <tuple>
 #include <utility>
 
@@ skipping 1839 matching lines @@
 
   IPC::IpcSecurityTestUtil::PwnMessageReceived(
       process->GetChannel(),
       FileSystemHostMsg_Write(request_id, file_path, blob_uuid, position));
 
   // If this started an async operation, wait for it to complete.
   if (waiter.did_start_update())
     waiter.WaitForEndUpdate();
 }
 
+void RegisterDragStartCallback(DragStartCallback callback) {
+  RenderWidgetHostImpl::RegisterDragStartCallbackForTesting(
+      std::move(callback));
+}
+
 }  // namespace content