Convert JsonWriter::Write to taking a const ref for the in-param

cc/trees/layer_tree_host_impl.cc

 // Copyright 2011 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/trees/layer_tree_host_impl.h"
 
 #include <algorithm>
 #include <limits>
 #include <map>
 #include <set>
@@ skipping 3093 matching lines @@
 
   if (animation_registrar_->ActivateAnimations())
     SetNeedsAnimate();
 }
 
 std::string LayerTreeHostImpl::LayerTreeAsJson() const {
   std::string str;
   if (active_tree_->root_layer()) {
     scoped_ptr<base::Value> json(active_tree_->root_layer()->LayerTreeAsJson());
     base::JSONWriter::WriteWithOptions(
-        json.get(), base::JSONWriter::OPTIONS_PRETTY_PRINT, &str);
+        *json, base::JSONWriter::OPTIONS_PRETTY_PRINT, &str);
   }
   return str;
 }
 
 int LayerTreeHostImpl::SourceAnimationFrameNumber() const {
   return fps_counter_->current_frame_number();
 }
 
 void LayerTreeHostImpl::StartAnimatingScrollbarAnimationController(
     ScrollbarAnimationController* controller) {
@@ skipping 296 matching lines @@
   new_target.SetToMin(layer_impl->MaxScrollOffset());
 
   curve->UpdateTarget(
       animation->TrimTimeToCurrentIteration(CurrentBeginFrameArgs().frame_time)
           .InSecondsF(),
       new_target);
 
   return true;
 }
 }  // namespace cc