Change LayerImpl::LayerTreeAsJson to return a std::unique_ptr.

cc/layers/ui_resource_layer_impl.cc

 // Copyright 2013 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/layers/ui_resource_layer_impl.h"
 
 #include "base/strings/stringprintf.h"
 #include "base/values.h"
 #include "cc/base/math_util.h"
 #include "cc/quads/texture_draw_quad.h"
@@ skipping 122 matching lines @@
                resource, premultiplied_alpha, uv_top_left_, uv_bottom_right_,
                SK_ColorTRANSPARENT, vertex_opacity_, flipped, nearest_neighbor,
                false);
   ValidateQuadResources(quad);
 }
 
 const char* UIResourceLayerImpl::LayerTypeAsString() const {
   return "cc::UIResourceLayerImpl";
 }
 
-base::DictionaryValue* UIResourceLayerImpl::LayerTreeAsJson() const {
-  base::DictionaryValue* result = LayerImpl::LayerTreeAsJson();
+std::unique_ptr<base::DictionaryValue> UIResourceLayerImpl::LayerTreeAsJson()
+    const {
+  std::unique_ptr<base::DictionaryValue> result = LayerImpl::LayerTreeAsJson();
 
   result->Set("ImageBounds", MathUtil::AsValue(image_bounds_).release());
 
   base::ListValue* list = new base::ListValue;
   list->AppendDouble(vertex_opacity_[0]);
   list->AppendDouble(vertex_opacity_[1]);
   list->AppendDouble(vertex_opacity_[2]);
   list->AppendDouble(vertex_opacity_[3]);
   result->Set("VertexOpacity", list);
 
   result->Set("UVTopLeft", MathUtil::AsValue(uv_top_left_).release());
   result->Set("UVBottomRight", MathUtil::AsValue(uv_bottom_right_).release());
 
   return result;
 }
 
 }  // namespace cc