Remove unnecessary Document.h includes in .cpp files

Source/core/dom/MainThreadTaskRunner.cpp

 /*
  * Copyright (C) 2013 Google Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  */
 
 #include "config.h"
 #include "core/dom/MainThreadTaskRunner.h"
 
-#include "core/dom/Document.h"
+#include "core/dom/ExecutionContext.h"
 #include "core/dom/ExecutionContextTask.h"
 #include "wtf/Assertions.h"
+#include "wtf/MainThread.h"
 
 namespace WebCore {
 
 struct PerformTaskContext {
     WTF_MAKE_NONCOPYABLE(PerformTaskContext); WTF_MAKE_FAST_ALLOCATED;
 public:
     PerformTaskContext(WeakPtr<MainThreadTaskRunner> runner, PassOwnPtr<ExecutionContextTask> task, bool isInspectorTask)
         : m_runner(runner)
         , m_task(task)
         , m_isInspectorTask(isInspectorTask)
@@ skipping 71 matching lines @@
 void MainThreadTaskRunner::pendingTasksTimerFired(Timer<MainThreadTaskRunner>*)
 {
     while (!m_pendingTasks.isEmpty()) {
         OwnPtr<ExecutionContextTask> task = m_pendingTasks[0].release();
         m_pendingTasks.remove(0);
         task->performTask(m_context);
     }
 }
 
 } // namespace