Delivering the FIRST_NONEMPTY_PAINT phase changing event to base/

components/metrics/profiler/tracking_synchronizer_observer.h

Index: components/metrics/profiler/tracking_synchronizer_observer.h
diff --git a/components/metrics/profiler/tracking_synchronizer_observer.h b/components/metrics/profiler/tracking_synchronizer_observer.h
index 0e943508079bd814169fae18b759ff563f74c21f..c9f88a73d41a1a16d3d31b757d7bb754cb78b1cc 100644
--- a/components/metrics/profiler/tracking_synchronizer_observer.h
+++ b/components/metrics/profiler/tracking_synchronizer_observer.h
@@ -8,6 +8,7 @@
 #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"
 
@@ -26,31 +27,46 @@ namespace metrics {
 // efficient.
 typedef std::vector<ProfilerEventProto::ProfilerEvent> ProfilerEvents;
 
+// Attributes of profiler data passed to
+// TrackingSynchronizerObserver::ReceivedProfilerData.
+struct ProfilerDataAttributes {
+  ProfilerDataAttributes(int profiling_phase,
+                         base::ProcessId process_id,
+                         content::ProcessType process_type,
+                         base::TimeTicks phase_start,
+                         base::TimeTicks phase_finish);
+
+  // 0-indexed profiling phase number.
+  const int profiling_phase;
+
+  // ID of the process that reported the data.
+  const base::ProcessId process_id;
+
+  // Type of the process that reported the data.
+  const content::ProcessType process_type;
+
+  // Time of the profiling phase start.
+  const base::TimeTicks phase_start;
+
+  // Time of the profiling phase finish.
+  const base::TimeTicks phase_finish;
+};
+
 // 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.
+  // Received |process_data_phase| for profiling phase and process defined by
+  // |attributes|.
+  // 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 ProfilerDataAttributes& attributes,
       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,
       const ProfilerEvents& past_events) = 0;
 
   // The observer should not expect any more calls to |ReceivedProfilerData()|