tracing: Make ConvertableToTraceFormat move-only scoped_ptr

cc/layers/layer_impl.cc

 // Copyright 2012 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/layer_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <utility>
@@ skipping 185 matching lines @@
     return;
 
   if (parent)
     DCHECK_EQ(layer_tree_impl()->LayerById(parent->id()), parent);
 
   scroll_parent_ = parent;
   SetNeedsPushProperties();
 }
 
 void LayerImpl::SetDebugInfo(
-    scoped_refptr<base::trace_event::ConvertableToTraceFormat> other) {
-  debug_info_ = other;
+    scoped_ptr<base::trace_event::ConvertableToTraceFormat> other) {
+  debug_info_ = std::move(other);
   SetNeedsPushProperties();
 }
 
 void LayerImpl::SetScrollChildren(std::set<LayerImpl*>* children) {
   if (scroll_children_.get() == children)
     return;
   scroll_children_.reset(children);
   SetNeedsPushProperties();
 }
 
@@ skipping 384 matching lines @@
 
   layer->PassCopyRequests(&copy_requests_);
 
   // If the main thread commits multiple times before the impl thread actually
   // draws, then damage tracking will become incorrect if we simply clobber the
   // update_rect here. The LayerImpl's update_rect needs to accumulate (i.e.
   // union) any update changes that have occurred on the main thread.
   update_rect_.Union(layer->update_rect());
   layer->SetUpdateRect(update_rect_);
 
-  layer->SetDebugInfo(debug_info_);
+  layer->SetDebugInfo(std::move(debug_info_));

[danakj, 2016/02/25 23:10:07]

For future archeologists. I don't see us tracing this info on the pending tree
ever currently, and if we only trace it for layers that have something novel
from the active tree that is probably okay too.

If it ends up being some serious problem, we could have the pending tree trace
its active twin's debug_info_ also.

 
   if (frame_timing_requests_dirty_) {
     layer->SetFrameTimingRequests(frame_timing_requests_);
     frame_timing_requests_dirty_ = false;
   }
 
   // Reset any state that should be cleared for the next update.
   layer_property_changed_ = false;
   update_rect_ = gfx::Rect();
   needs_push_properties_ = false;
@@ skipping 1155 matching lines @@
            .layer_transforms_should_scale_layer_contents) {
     return default_scale;
   }
 
   gfx::Vector2dF transform_scales = MathUtil::ComputeTransform2dScaleComponents(
       DrawTransform(), default_scale);
   return std::max(transform_scales.x(), transform_scales.y());
 }
 
 }  // namespace cc