Make cc::DrawingDisplayItem hold a const SkPicture.

cc/blink/web_display_item_list_impl.cc

 // 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 "cc/blink/web_display_item_list_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <vector>
@@ skipping 36 matching lines @@
 WebDisplayItemListImpl::WebDisplayItemListImpl(
     cc::DisplayItemList* display_list)
     : display_item_list_(display_list) {
 }
 
 void WebDisplayItemListImpl::appendDrawingItem(
     const blink::WebRect& visual_rect,
     const SkPicture* picture) {
   if (display_item_list_->RetainsIndividualDisplayItems()) {
     display_item_list_->CreateAndAppendItem<cc::DrawingDisplayItem>(
-        visual_rect, skia::SharePtr(const_cast<SkPicture*>(picture)));
+        visual_rect, skia::SharePtr(picture));
   } else {
-    cc::DrawingDisplayItem item(
-        skia::SharePtr(const_cast<SkPicture*>(picture)));
+    cc::DrawingDisplayItem item(skia::SharePtr(picture));
     display_item_list_->RasterIntoCanvas(item);
   }
 }
 
 void WebDisplayItemListImpl::appendClipItem(
     const blink::WebRect& visual_rect,
     const blink::WebRect& clip_rect,
     const blink::WebVector<SkRRect>& rounded_clip_rects) {
   std::vector<SkRRect> rounded_rects;
   for (size_t i = 0; i < rounded_clip_rects.size(); ++i) {
@@ skipping 162 matching lines @@
 
 void WebDisplayItemListImpl::appendEndScrollItem(
     const blink::WebRect& visual_rect) {
   appendEndTransformItem(visual_rect);
 }
 
 WebDisplayItemListImpl::~WebDisplayItemListImpl() {
 }
 
 }  // namespace cc_blink