content: Cleanup class/struct forward declarations

content/renderer/render_widget.h

 // 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.
 
 #ifndef CONTENT_RENDERER_RENDER_WIDGET_H_
 #define CONTENT_RENDERER_RENDER_WIDGET_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 42 matching lines @@
 #include "ui/base/ui_base_types.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/vector2d_f.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/gfx/range/range.h"
 #include "ui/surface/transport_dib.h"
 
 class GURL;
 
 namespace IPC {
-class SyncMessage;
 class SyncMessageFilter;
 }
 
 namespace blink {
 namespace scheduler {
 class RenderWidgetSchedulingState;
 }
 struct WebDeviceEmulationParams;
 class WebDragData;
 class WebFrameWidget;
 class WebGestureEvent;
 class WebImage;
 class WebInputMethodController;
 class WebLocalFrame;
 class WebMouseEvent;
 class WebNode;
 struct WebPoint;
 }
 
 namespace cc {
 class CompositorFrameSink;
-class FrameSinkId;
 class SwapPromise;
 }
 
 namespace gfx {
 class Range;
 }
 
 namespace ui {
 struct DidOverscrollParams;
 }
@@ skipping 763 matching lines @@
   // being handled. If the current event results in starting a drag/drop
   // session, this info is sent to the browser along with other drag/drop info.
   DragEventSourceInfo possible_drag_event_info_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidget);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_RENDER_WIDGET_H_