Add the tracing manager

chrome/browser/feedback/tracing_manager.h

Index: chrome/browser/feedback/tracing_manager.h
diff --git a/chrome/browser/feedback/tracing_manager.h b/chrome/browser/feedback/tracing_manager.h
new file mode 100644
index 0000000000000000000000000000000000000000..2a2fa315c72e48df204d3c3570f921afb47e70c1
--- /dev/null
+++ b/chrome/browser/feedback/tracing_manager.h
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+// Copyright (c) 2013 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 CHROME_BROWSER_FEEDBACK_TRACING_MANAGER_H_
+#define CHROME_BROWSER_FEEDBACK_TRACING_MANAGER_H_
+
+#include <map>
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/callback.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
+#include "content/public/browser/trace_subscriber.h"
+
+// Callback used for getting the output of a trace.
+typedef base::Callback<void(scoped_refptr<base::RefCountedString> trace_data)>
+    TraceDataCallback;
+
+// This class is used to manage performance meterics that can be attached to
+// feedback reports.  This class is a Singleton that is owned by the preference
+// system.  It should only be created when it is enabled, and should only be
+// accessed elsewhere via Get().
+//
+// When a performance trace is desired, TracingManager::Get()->RequestTrace()
+// should be invoked.  The TracingManager will then start preparing a zipped
+// version of the performance data.  That data can then be requested via
+// GetTraceData().  When the data is no longer needed, it should be discarded
+// via DiscardTraceData().
+class TracingManager : public content::TraceSubscriber {
+ public:
+  virtual ~TracingManager();
+
+  // Create a TracingManager.  Can only be called when none exists.
+  static scoped_ptr<TracingManager> Create();
+
+  // Get the current TracingManager.  Returns NULL if one doesn't exist.
+  static TracingManager* Get();
+
+  // Request a trace ending at the current time.  If a trace is already being
+  // collected, the id for that trace is returned.
+  int RequestTrace();
+
+  // Get the trace data for |id|.  On success, true is returned, and the data is
+  // returned via |callback|.  Returns false on failure.
+  bool GetTraceData(int id, const TraceDataCallback& callback);
+
+  // Discard the data for trace |id|.
+  void DiscardTraceData(int id);
+
+ private:
+  void StartTracing();
+
+  // content::TraceSubscriber overrides
+  virtual void OnEndTracingComplete() OVERRIDE;
+  virtual void OnTraceDataCollected(
+      const scoped_refptr<base::RefCountedString>& trace_fragment) OVERRIDE;
+
+  TracingManager();
+
+  // Data being collected from the current trace.
+  std::string data_;
+
+  // ID of the trace that is being collected.
+  int current_trace_id_;
+
+  // Mapping of trace ID to trace data.
+  std::map<int, scoped_refptr<base::RefCountedString> > trace_data_;
+
+  // Callback for the current trace request.
+  TraceDataCallback trace_callback_;
+
+  base::WeakPtrFactory<TracingManager> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(TracingManager);
+};
+
+#endif  // CHROME_BROWSER_FEEDBACK_TRACING_MANAGER_H_
+