Delivering the FIRST_NONEMPTY_PAINT phase changing event to base/

components/metrics/profiler/tracking_synchronizer_observer.h

 // Copyright (c) 2012 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 COMPONENTS_METRICS_PROFILER_TRACKING_SYNCHRONIZER_OBSERVER_H_
 #define COMPONENTS_METRICS_PROFILER_TRACKING_SYNCHRONIZER_OBSERVER_H_
 
 #include <vector>
 
 #include "base/process/process_handle.h"
+#include "base/time/time.h"
 #include "components/metrics/proto/chrome_user_metrics_extension.pb.h"
 #include "content/public/common/process_type.h"
 
 namespace base {
 class TimeDelta;
 }
 
 namespace tracked_objects {
 struct ProcessDataPhaseSnapshot;
 }
 
 namespace metrics {
 
 // Set of profiling events, in no guaranteed order. Implemented as a vector
 // because we don't need to have an efficient .find() on it, so vector<> is more
 // efficient.
 typedef std::vector<ProfilerEventProto::ProfilerEvent> ProfilerEvents;
 
 // Observer for notifications from the TrackingSynchronizer class.
 class TrackingSynchronizerObserver {
  public:
-  // TODO(vadimt): Consider isherman@ idea: I'd change the phase_start and
-  // phase_finish from TimeDeltas to TimeTicks.  And I'd omit the |past_events|
-  // list -- either in favor of a single ProfilerEvent that corresponds to the
-  // phase, or a method on the TrackingSynchronizer that can translate a
-  // profiling_phase to a ProfilerEvent.
-
   // Received |process_data_phase| for profiling phase |profiling_phase| from a
-  // single process of |process_type|. The phase start and finish times,
-  // relative to the start time are |phase_start| and
-  // |phase_finish|. All profiling phases prior to the reported one have already
-  // completed, and each completion was associated with an instance of
-  // ProfilerEventProto::ProfilerEvent. |past_events| contains events associated
-  // with completions of phases prior to the reported one.
+  // single process of |process_type|. The phase start and finish times are
+  // |phase_start| and |phase_finish|.
+  // Each completed phase is associated with an event that triggered the
+  // completion of the phase. |past_events| contains the set of events that
+  // completed prior to the reported phase. This data structure is useful for
+  // quickly computing the full set of profiled traces that occurred before or
+  // after a given event.
   // The observer should assume there might be more data coming until
   // FinishedReceivingData() is called.
   virtual void ReceivedProfilerData(
       const tracked_objects::ProcessDataPhaseSnapshot& process_data_phase,
       base::ProcessId process_id,
       content::ProcessType process_type,
       int profiling_phase,
-      base::TimeDelta phase_start,
-      base::TimeDelta phase_finish,
+      base::TimeTicks phase_start,
+      base::TimeTicks phase_finish,
       const ProfilerEvents& past_events) = 0;
 
   // The observer should not expect any more calls to |ReceivedProfilerData()|
   // (without re-registering).  This is sent either when data from all processes
   // has been gathered, or when the request times out.
   virtual void FinishedReceivingProfilerData() {}
 
  protected:
   TrackingSynchronizerObserver() {}
   virtual ~TrackingSynchronizerObserver() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(TrackingSynchronizerObserver);
 };
 
 }  // namespace metrics
 
 #endif  // COMPONENTS_METRICS_PROFILER_TRACKING_SYNCHRONIZER_OBSERVER_H_