[Tracing] Update sync_id to be string type for clock sync

content/browser/tracing/power_tracing_agent.h

 // Copyright 2015 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_TRACING_POWER_TRACING_AGENT_H_
 #define CONTENT_BROWSER_TRACING_POWER_TRACING_AGENT_H_
 
 #include "base/macros.h"
 #include "base/memory/ref_counted_memory.h"
 #include "base/threading/thread.h"
@@ skipping 16 matching lines @@
   // base::trace_event::TracingAgent implementation.
   std::string GetTracingAgentName() override;
   std::string GetTraceEventLabel() override;
 
   void StartAgentTracing(const base::trace_event::TraceConfig& trace_config,
                          const StartAgentTracingCallback& callback) override;
   void StopAgentTracing(const StopAgentTracingCallback& callback) override;
 
   bool SupportsExplicitClockSync() override;
   void RecordClockSyncMarker(
-      int sync_id,
+      const std::string& sync_id,
       const RecordClockSyncMarkerCallback& callback) override;
 
  private:
   // This allows constructor and destructor to be private and usable only
   // by the Singleton class.
   friend struct base::DefaultSingletonTraits<PowerTracingAgent>;
 
   // Constructor.
   PowerTracingAgent();
   ~PowerTracingAgent() override;
 
   void OnStopTracingDone(const StopAgentTracingCallback& callback,
                          const scoped_refptr<base::RefCountedString>& result);
 
   void TraceOnThread();
   void FlushOnThread(const StopAgentTracingCallback& callback);
   void RecordClockSyncMarkerOnThread(
-      int sync_id,
+      const std::string& sync_id,
       const RecordClockSyncMarkerCallback& callback);
 
   base::Thread thread_;
   scoped_ptr<BattorPowerTraceProvider> battor_trace_provider_;
 
   DISALLOW_COPY_AND_ASSIGN(PowerTracingAgent);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_TRACING_POWER_TRACING_AGENT_H_