Constify SkPicture in DrawingDisplayItem (cc side)

cc/blink/web_display_item_list_impl.h

 // 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.
 
 #ifndef CC_BLINK_WEB_DISPLAY_ITEM_LIST_IMPL_H_
 #define CC_BLINK_WEB_DISPLAY_ITEM_LIST_IMPL_H_
 
 #include "base/memory/ref_counted.h"
 #include "cc/blink/cc_blink_export.h"
 #include "cc/resources/display_item_list.h"
 #include "third_party/WebKit/public/platform/WebBlendMode.h"
 #include "third_party/WebKit/public/platform/WebContentLayerClient.h"
 #include "third_party/WebKit/public/platform/WebDisplayItemList.h"
 #include "third_party/WebKit/public/platform/WebFloatPoint.h"
 #include "third_party/WebKit/public/platform/WebVector.h"
 #include "third_party/skia/include/core/SkRegion.h"
+#include "ui/gfx/geometry/point_f.h"
 
 class SkImageFilter;
 class SkMatrix44;
 class SkPath;
 class SkPicture;
 class SkRRect;
 
 namespace cc_blink {
 
 class WebDisplayItemListImpl : public blink::WebDisplayItemList {
  public:
   CC_BLINK_EXPORT WebDisplayItemListImpl();
   virtual ~WebDisplayItemListImpl();
 
   scoped_refptr<cc::DisplayItemList> ToDisplayItemList();
 
   // blink::WebDisplayItemList implementation.
-  virtual void appendDrawingItem(SkPicture* picture,
-                                 const blink::WebFloatPoint& location);
+  virtual void appendDrawingItem(
+      const SkPicture*,
+      const blink::WebFloatPoint& location = gfx::PointF());
   virtual void appendClipItem(
       const blink::WebRect& clip_rect,
       const blink::WebVector<SkRRect>& rounded_clip_rects);
   virtual void appendEndClipItem();
   virtual void appendClipPathItem(const SkPath& clip_path,
                                   SkRegion::Op clip_op,
                                   bool antialias);
   virtual void appendEndClipPathItem();
   virtual void appendFloatClipItem(const blink::WebFloatRect& clip_rect);
   virtual void appendEndFloatClipItem();
   virtual void appendTransformItem(const SkMatrix44& matrix);
   virtual void appendEndTransformItem();
   virtual void appendTransparencyItem(float opacity,
                                       blink::WebBlendMode blend_mode);
   virtual void appendEndTransparencyItem();
   virtual void appendFilterItem(SkImageFilter* filter,
                                 const blink::WebFloatRect& bounds);
   virtual void appendEndFilterItem();
 
  private:
   scoped_refptr<cc::DisplayItemList> display_item_list_;
 
   DISALLOW_COPY_AND_ASSIGN(WebDisplayItemListImpl);
 };
 
 }  // namespace cc_blink
 
 #endif  // CC_BLINK_WEB_DISPLAY_ITEM_LIST_IMPL_H_