Constify SkPicture in DrawingDisplayItem (cc side)

cc/blink/web_display_item_list_impl.cc

Index: cc/blink/web_display_item_list_impl.cc
diff --git a/cc/blink/web_display_item_list_impl.cc b/cc/blink/web_display_item_list_impl.cc
index fdd05df63ab80407c5c19a84e7dfefe90e00fd2b..d6b100b326e4ef028de1e9c0d82143504a0025c6 100644
--- a/cc/blink/web_display_item_list_impl.cc
+++ b/cc/blink/web_display_item_list_impl.cc
@@ -33,10 +33,17 @@ scoped_refptr<cc::DisplayItemList> WebDisplayItemListImpl::ToDisplayItemList() {
 }
 
 void WebDisplayItemListImpl::appendDrawingItem(
+    const SkPicture* picture,
+    const blink::WebFloatPoint& location) {
+  display_item_list_->AppendItem(
+      cc::DrawingDisplayItem::Create(skia::SharePtr(picture)));
+}
+
+void WebDisplayItemListImpl::appendDrawingItem(
     SkPicture* picture,
     const blink::WebFloatPoint& location) {
   display_item_list_->AppendItem(
-      cc::DrawingDisplayItem::Create(skia::SharePtr(picture), location));
+      cc::DrawingDisplayItem::Create(skia::SharePtr(picture)));
 }
 
 void WebDisplayItemListImpl::appendClipItem(