Implement about:tracing UI for the sampling profiler (Chromium part)

base/debug/trace_event_impl.h

Index: base/debug/trace_event_impl.h
diff --git a/base/debug/trace_event_impl.h b/base/debug/trace_event_impl.h
index e1bf148581627d1be976015380ca16f3700c6be8..3668cfb2367e5e7b7b04a86d906e63e6ecf0fa02 100644
--- a/base/debug/trace_event_impl.h
+++ b/base/debug/trace_event_impl.h
@@ -155,6 +155,7 @@ class BASE_EXPORT TraceBuffer {
   virtual size_t Size() const = 0;
   virtual size_t Capacity() const = 0;
   virtual const TraceEvent& GetEventAt(size_t index) const = 0;
+  virtual TraceBuffer* Clone() const = 0;
 };
 
 // TraceResultBuffer collects and converts trace fragments returned by TraceLog
@@ -318,10 +319,16 @@ class BASE_EXPORT TraceLog {
   // on how to control what categories will be traced.
   void SetEnabled(const CategoryFilter& category_filter, Options options);
 
-  // Disable tracing for all categories.
+  // Disables tracing for all categories.
   void SetDisabled();
   bool IsEnabled() { return !!enable_count_; }
 
+  // Enables continuous sampling tracing.
+  void SetContinuousSamplingEnabled();
+
+  // Disables continuous sampling tracing.
+  void SetContinuousSamplingDisabled();
+
   // The number of times we have begun recording traces. If tracing is off,
   // returns -1. If tracing is on, then it returns the number of times we have
   // recorded a trace. By watching for this number to increment, you can
@@ -384,6 +391,7 @@ class BASE_EXPORT TraceLog {
   typedef base::Callback<void(const scoped_refptr<base::RefCountedString>&)>
       OutputCallback;
   void Flush(const OutputCallback& cb);
+  void FlushContinuousSamplingTracing(const OutputCallback& cb);
 
   // Called by TRACE_EVENT* macros, don't call this directly.
   // The name parameter is a category group for example:
@@ -442,6 +450,8 @@ class BASE_EXPORT TraceLog {
   // Exposed for unittesting:
 
   void InstallWaitableEventForSamplingTesting(WaitableEvent* waitable_event);
+  void InstallWaitableEventForContinuousSamplingTesting(
+      WaitableEvent* waitable_event);
 
   // Allows deleting our singleton instance.
   static void DeleteForTesting();
@@ -532,7 +542,7 @@ class BASE_EXPORT TraceLog {
   TraceLog();
   ~TraceLog();
   const unsigned char* GetCategoryGroupEnabledInternal(const char* name);
-  void AddMetadataEvents();
+  void AddMetadataEvents(unsigned char flags);
 
 #if defined(OS_ANDROID)
   void SendToATrace(char phase,
@@ -555,9 +565,11 @@ class BASE_EXPORT TraceLog {
   // This lock protects TraceLog member accesses from arbitrary threads.
   Lock lock_;
   int enable_count_;
+  int continuous_sampling_enable_count_;
   int num_traces_recorded_;
   NotificationCallback notification_callback_;
   scoped_ptr<TraceBuffer> logged_events_;
+  scoped_ptr<TraceBuffer> continuous_sampling_logged_events_;
   EventCallback event_callback_;
   bool dispatching_to_observer_list_;
   std::vector<EnabledStateObserver*> enabled_state_observer_list_;
@@ -588,6 +600,13 @@ class BASE_EXPORT TraceLog {
   scoped_ptr<TraceSamplingThread> sampling_thread_;
   PlatformThreadHandle sampling_thread_handle_;
 
+  // Continuous sampling thread handles.
+  // TODO(haraken): Merge this thread with the normal sampling thread.
+  //                Currently we launch two sampling threads when we
+  //                record normal tracing with enabling continuous sampling.
+  scoped_ptr<TraceSamplingThread> continuous_sampling_thread_;
+  PlatformThreadHandle continuous_sampling_thread_handle_;
+
   CategoryFilter category_filter_;
 
   DISALLOW_COPY_AND_ASSIGN(TraceLog);