cc: Make DisplayItemList::Append replay into an SkPicture

cc/trees/layer_tree_host_common_unittest.cc

Index: cc/trees/layer_tree_host_common_unittest.cc
diff --git a/cc/trees/layer_tree_host_common_unittest.cc b/cc/trees/layer_tree_host_common_unittest.cc
index 439d9200a911013def3d661b844531acffee0b08..0046b1a3c41a061d672388060f4235c3919d79c5 100644
--- a/cc/trees/layer_tree_host_common_unittest.cc
+++ b/cc/trees/layer_tree_host_common_unittest.cc
@@ -60,11 +60,11 @@ class MockContentLayerClient : public ContentLayerClient {
   void PaintContents(SkCanvas* canvas,
                      const gfx::Rect& clip,
                      PaintingControlSetting picture_control) override {}
-  scoped_refptr<DisplayItemList> PaintContentsToDisplayList(
+  void PaintContentsToDisplayList(
+      DisplayItemList* display_list,
       const gfx::Rect& clip,
       PaintingControlSetting picture_control) override {
     NOTIMPLEMENTED();
-    return DisplayItemList::Create();
   }
   bool FillsBoundsCompletely() const override { return false; }
 };