Remove unnecessary Document.h includes in .cpp files

Source/web/tests/WebDocumentTest.cpp

 // Copyright 2014 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 "config.h"
 
 #include "public/web/WebDocument.h"
 
 #include "core/CSSPropertyNames.h"
-#include "core/dom/Document.h"
 #include "core/dom/NodeRenderStyle.h"
 #include "core/frame/LocalFrame.h"
 #include "core/html/HTMLElement.h"
 #include "core/page/Page.h"
 #include "core/rendering/style/RenderStyle.h"
 #include "platform/graphics/Color.h"
 #include "web/tests/FrameTestHelpers.h"
 
 #include <gtest/gtest.h>
 
@@ skipping 33 matching lines @@
     coreDoc->updateRenderTreeIfNeeded();
 
     style = bodyElement->renderStyle();
     ASSERT(style);
 
     // Inserted stylesheet applied.
     ASSERT_EQ(Color(0, 128, 0), style->visitedDependentColor(WebCore::CSSPropertyColor));
 }
 
 }