Don't include headers from the layout API from other headers needlessly.

third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.cpp

 // 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.
 
 #include "core/offscreencanvas/OffscreenCanvas.h"
 
 #include "core/dom/ExceptionCode.h"
 #include "core/html/canvas/CanvasContextCreationAttributes.h"
 #include "core/html/canvas/CanvasRenderingContext.h"
 #include "core/html/canvas/CanvasRenderingContextFactory.h"
+#include "platform/graphics/Image.h"
 #include "platform/graphics/ImageBuffer.h"
 #include "platform/graphics/OffscreenCanvasFrameDispatcherImpl.h"
 #include "wtf/MathExtras.h"
 #include <memory>
 
 namespace blink {
 
 OffscreenCanvas::OffscreenCanvas(const IntSize& size)
     : m_size(size)
     , m_originClean(true)
@@ skipping 127 matching lines @@
         m_frameDispatcher = wrapUnique(new OffscreenCanvasFrameDispatcherImpl(m_clientId, m_localId, m_nonce, width(), height()));
     return m_frameDispatcher.get();
 }
 
 DEFINE_TRACE(OffscreenCanvas)
 {
     visitor->trace(m_context);
 }
 
 } // namespace blink