Make incremental marking tracing format consistent with GC tracing.

src/heap/gc-tracer.h

 // Copyright 2014 the V8 project 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 V8_HEAP_GC_TRACER_H_
 #define V8_HEAP_GC_TRACER_H_
 
 #include "src/base/compiler-specific.h"
 #include "src/base/platform/platform.h"
 #include "src/counters.h"
@@ skipping 363 matching lines @@
   // events.
   // Returns 0 if no events have been recorded.
   double AverageSurvivalRatio() const;
 
   // Returns true if at least one survival event was recorded.
   bool SurvivalEventsRecorded() const;
 
   // Discard all recorded survival events.
   void ResetSurvivalEvents();
 
+  void NotifyIncrementalMarkingStart();
+
   V8_INLINE void AddScopeSample(Scope::ScopeId scope, double duration) {
     DCHECK(scope < Scope::NUMBER_OF_SCOPES);
     if (scope >= Scope::FIRST_INCREMENTAL_SCOPE &&
         scope <= Scope::LAST_INCREMENTAL_SCOPE) {
       incremental_marking_scopes_[scope].Update(duration);
     } else {
       current_.scopes[scope] += duration;
     }
   }
 
@@ skipping 75 matching lines @@
 
   // Total sweeping time on the main thread.
   // This timer is precise when run with --print-cumulative-gc-stat
   // TODO(hpayer): Account for sweeping time on sweeper threads. Add a
   // different field for that.
   // TODO(hpayer): This timer right now just holds the sweeping time
   // of the initial atomic sweeping pause. Make sure that it accumulates
   // all sweeping operations performed on the main thread.
   double cumulative_sweeping_duration_;
 
+  double incremental_marking_start_time_;
+
   // Timestamp and allocation counter at the last sampled allocation event.
   double allocation_time_ms_;
   size_t new_space_allocation_counter_bytes_;
   size_t old_generation_allocation_counter_bytes_;
 
   // Accumulated duration and allocated bytes since the last GC.
   double allocation_duration_since_gc_;
   size_t new_space_allocation_in_bytes_since_gc_;
   size_t old_generation_allocation_in_bytes_since_gc_;
 
@@ skipping 15 matching lines @@
   RingBuffer<BytesAndDuration> recorded_old_generation_allocations_;
   RingBuffer<double> recorded_context_disposal_times_;
   RingBuffer<double> recorded_survival_ratios_;
 
   DISALLOW_COPY_AND_ASSIGN(GCTracer);
 };
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_GC_TRACER_H_