[heap] Add histogram timers for incremental marking start and finalization event.

src/heap/incremental-marking.cc

 // Copyright 2012 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.
 
 #include "src/heap/incremental-marking.h"
 
 #include "src/code-stubs.h"
 #include "src/compilation-cache.h"
 #include "src/conversions.h"
 #include "src/heap/gc-idle-time-handler.h"
@@ skipping 538 matching lines @@
 void IncrementalMarking::Start(const char* reason) {
   if (FLAG_trace_incremental_marking) {
     PrintF("[IncrementalMarking] Start (%s)\n",
            (reason == nullptr) ? "unknown reason" : reason);
   }
   DCHECK(FLAG_incremental_marking);
   DCHECK(state_ == STOPPED);
   DCHECK(heap_->gc_state() == Heap::NOT_IN_GC);
   DCHECK(!heap_->isolate()->serializer_enabled());
 
+  HistogramTimerScope incremental_marking_scope(
+      heap_->isolate()->counters()->gc_incremental_marking_start());
   ResetStepCounters();
 
   was_activated_ = true;
 
   if (!heap_->mark_compact_collector()->sweeping_in_progress()) {
     StartMarking();
   } else {
     if (FLAG_trace_incremental_marking) {
       PrintF("[IncrementalMarking] Start sweeping.\n");
     }
@@ skipping 583 matching lines @@
 void IncrementalMarking::IncrementIdleMarkingDelayCounter() {
   idle_marking_delay_counter_++;
 }
 
 
 void IncrementalMarking::ClearIdleMarkingDelayCounter() {
   idle_marking_delay_counter_ = 0;
 }
 }  // namespace internal
 }  // namespace v8