Remove BindStateHolder and have Bind() return a Callback<> object directly.

base/debug/trace_event.cc

 // Copyright (c) 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 "base/debug/trace_event.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/format_macros.h"
@@ skipping 278 matching lines @@
     const std::string& json_trace_output) {
   json_output += json_trace_output;
 }
 
 TraceResultBuffer::TraceResultBuffer() : append_comma_(false) {
 }
 
 TraceResultBuffer::~TraceResultBuffer() {
 }
 
-void TraceResultBuffer::SetOutputCallback(OutputCallback json_chunk_callback) {
+void TraceResultBuffer::SetOutputCallback(
+    const OutputCallback& json_chunk_callback) {
   output_callback_ = json_chunk_callback;
 }
 
 void TraceResultBuffer::Start() {
   append_comma_ = false;
   output_callback_.Run("[");
 }
 
 void TraceResultBuffer::AddFragment(const std::string& trace_fragment) {
   if (append_comma_)
@@ skipping 409 matching lines @@
         kNoArgName, kNoArgValue, kNoArgName, kNoArgValue,
         p_data_->threshold_begin_id, p_data_->threshold,
         TRACE_EVENT_FLAG_NONE);
   }
 }
 
 }  // namespace internal
 
 }  // namespace debug
 }  // namespace base