Revert of Make WebTraceLocation be an alias of tracked_objects::Location

third_party/WebKit/Source/platform/threading/BackgroundTaskRunner.h

 // Copyright 2015 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.
 
 #ifndef BackgroundTaskRunner_h
 #define BackgroundTaskRunner_h
 
 #include "platform/PlatformExport.h"
-#include "public/platform/WebTraceLocation.h"
 #include "wtf/Functional.h"
 
 namespace blink {
 
+class WebTraceLocation;
+
 namespace BackgroundTaskRunner {
 
 enum TaskSize {
     TaskSizeShortRunningTask,
     TaskSizeLongRunningTask,
 };
 
 PLATFORM_EXPORT void postOnBackgroundThread(const WebTraceLocation&, std::unique_ptr<CrossThreadClosure>, TaskSize);
 
 } // BackgroundTaskRunner
 
 } // namespace blink
 
 #endif