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

src/counters.h

 // 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.
 
 #ifndef V8_COUNTERS_H_
 #define V8_COUNTERS_H_
 
 #include "include/v8.h"
 #include "src/allocation.h"
 #include "src/base/platform/elapsed-timer.h"
@@ skipping 478 matching lines @@
   /* Garbage collection timers. */                                            \
   HT(gc_compactor, V8.GCCompactor, 10000, MILLISECOND)                        \
   HT(gc_finalize, V8.GCFinalizeMC, 10000, MILLISECOND)                        \
   HT(gc_finalize_reduce_memory, V8.GCFinalizeMCReduceMemory, 10000,           \
      MILLISECOND)                                                             \
   HT(gc_scavenger, V8.GCScavenger, 10000, MILLISECOND)                        \
   HT(gc_context, V8.GCContext, 10000,                                         \
      MILLISECOND) /* GC context cleanup time */                               \
   HT(gc_idle_notification, V8.GCIdleNotification, 10000, MILLISECOND)         \
   HT(gc_incremental_marking, V8.GCIncrementalMarking, 10000, MILLISECOND)     \
+  HT(gc_incremental_marking_start, V8.GCIncrementalMarkingStart, 10000,       \
+     MILLISECOND)                                                             \
+  HT(gc_incremental_marking_finalize, V8.GCIncrementalMarkingFinalize, 10000, \
+     MILLISECOND)                                                             \
   HT(gc_low_memory_notification, V8.GCLowMemoryNotification, 10000,           \
      MILLISECOND)                                                             \
   /* Parsing timers. */                                                       \
   HT(parse, V8.ParseMicroSeconds, 1000000, MICROSECOND)                       \
   HT(parse_lazy, V8.ParseLazyMicroSeconds, 1000000, MICROSECOND)              \
   HT(pre_parse, V8.PreParseMicroSeconds, 1000000, MICROSECOND)                \
   /* Compilation times. */                                                    \
   HT(compile, V8.CompileMicroSeconds, 1000000, MICROSECOND)                   \
   HT(compile_eval, V8.CompileEvalMicroSeconds, 1000000, MICROSECOND)          \
   /* Serialization as part of compilation (code caching) */                   \
@@ skipping 377 matching lines @@
 
   explicit Counters(Isolate* isolate);
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(Counters);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COUNTERS_H_