Use SequencedWorkerPool for disk operations in TraceSubscriberStdio.

content/browser/trace_controller.h

 // 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.
 
 #ifndef CONTENT_BROWSER_TRACE_CONTROLLER_H_
 #define CONTENT_BROWSER_TRACE_CONTROLLER_H_
 
 #include <set>
 #include <string>
 #include <vector>
 
 #include "base/debug/trace_event.h"
+#include "base/memory/ref_counted_memory.h"
 #include "base/memory/singleton.h"
 #include "content/common/content_export.h"
 
 class CommandLine;
 class TraceMessageFilter;
 
 // Objects interested in receiving trace data derive from TraceSubscriber.
 // See also: trace_message_filter.h
 // See also: child_trace_message_filter.h
 class CONTENT_EXPORT TraceSubscriber {
  public:
   // Called once after TraceController::EndTracingAsync.
   virtual void OnEndTracingComplete() = 0;
   // Called 0 or more times between TraceController::BeginTracing and
   // OnEndTracingComplete. Use base::debug::TraceResultBuffer to convert one or
   // more trace fragments to JSON.
-  virtual void OnTraceDataCollected(const std::string& trace_fragment) = 0;
+  virtual void OnTraceDataCollected(
+      const scoped_refptr<base::RefCountedString>& trace_fragment) = 0;
   // Called once after TraceController::GetKnownCategoriesAsync.
   virtual void OnKnownCategoriesCollected(
       const std::set<std::string>& known_categories);
   virtual void OnTraceBufferPercentFullReply(float percent_full);
 
  protected:
   virtual ~TraceSubscriber();
 };
 
 // TraceController is used on the browser processes to enable/disable
@@ skipping 107 matching lines @@
         (subscriber_ == NULL || subscriber == subscriber_);
   }
 
   // Methods for use by TraceMessageFilter.
 
   void AddFilter(TraceMessageFilter* filter);
   void RemoveFilter(TraceMessageFilter* filter);
   void OnTracingBegan(TraceSubscriber* subscriber);
   void OnEndTracingAck(const std::vector<std::string>& known_categories);
   void OnTraceDataCollected(
-      const scoped_refptr<base::debug::TraceLog::RefCountedString>&
-          events_str_ptr);
+      const scoped_refptr<base::RefCountedString>& events_str_ptr);
   void OnTraceBufferFull();
   void OnTraceBufferPercentFullReply(float percent_full);
 
   FilterMap filters_;
   TraceSubscriber* subscriber_;
   // Pending acks for EndTracingAsync:
   int pending_end_ack_count_;
   // Pending acks for GetTraceBufferPercentFullAsync:
   int pending_bpf_ack_count_;
   float maximum_bpf_;
   bool is_tracing_;
   bool is_get_categories_;
   std::set<std::string> known_categories_;
   std::vector<std::string> included_categories_;
   std::vector<std::string> excluded_categories_;
 
   DISALLOW_COPY_AND_ASSIGN(TraceController);
 };
 
 #endif  // CONTENT_BROWSER_TRACE_CONTROLLER_H_