[heap] Fix runtimestats scope for top-level GC tasks.

Perf sheriffs: this is going to increase GC time in v8.runtimestats
benchmarks. That time was not accounted before.

Change-Id: I656aed7ec7f4fd9f29dd4a2eff44eb25a60f21ad
Reviewed-on: https://chromium-review.googlesource.com/626636
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47520}

src/counters.h

@@ -781,7 +781,6 @@ class RuntimeCallTimer final {
   V(FunctionPrototypeGetter)                        \
   V(FunctionPrototypeSetter)                        \
   V(GC_Custom_AllAvailableGarbage)                  \
-  V(GC_Custom_IncrementalMarkingJob)                \
   V(GC_Custom_IncrementalMarkingObserver)           \
   V(GC_Custom_SlowAllocateRaw)                      \
   V(GCEpilogueCallback)                             \

src/heap-symbols.h

@@ -269,6 +269,7 @@
 #define INCREMENTAL_SCOPES(F)                                      \
   /* MC_INCREMENTAL is the top-level incremental marking scope. */ \
   F(MC_INCREMENTAL)                                                \
+  F(MC_INCREMENTAL_START)                                          \
   F(MC_INCREMENTAL_SWEEPING)                                       \
   F(MC_INCREMENTAL_WRAPPER_PROLOGUE)                               \
   F(MC_INCREMENTAL_WRAPPER_TRACING)                                \

src/heap/incremental-marking-job.cc

@@ -42,9 +42,7 @@ void IncrementalMarkingJob::Task::Step(Heap* heap) {
 
 void IncrementalMarkingJob::Task::RunInternal() {
   VMState<GC> state(isolate());
-  TRACE_EVENT_CALL_STATS_SCOPED(isolate(), "v8.gc", "V8.Task");
-  RuntimeCallTimerScope runtime_timer(
-      isolate(), &RuntimeCallStats::GC_Custom_IncrementalMarkingJob);
+  TRACE_EVENT_CALL_STATS_SCOPED(isolate(), "v8", "V8.Task");
 
   Heap* heap = isolate()->heap();
   IncrementalMarking* incremental_marking = heap->incremental_marking();

src/heap/incremental-marking.cc

@@ -481,6 +481,7 @@ void IncrementalMarking::Start(GarbageCollectionReason gc_reason) {
   HistogramTimerScope incremental_marking_scope(
       counters->gc_incremental_marking_start());
   TRACE_EVENT0("v8", "V8.GCIncrementalMarkingStart");
+  TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_INCREMENTAL_START);
   heap_->tracer()->NotifyIncrementalMarkingStart();
 
   start_time_ms_ = heap()->MonotonicallyIncreasingTimeInMs();

src/heap/scavenge-job.cc

@@ -19,7 +19,7 @@ const double ScavengeJob::kMaxAllocationLimitAsFractionOfNewSpace = 0.8;
 
 void ScavengeJob::IdleTask::RunInternal(double deadline_in_seconds) {
   VMState<GC> state(isolate());
-  TRACE_EVENT_CALL_STATS_SCOPED(isolate(), "v8.gc", "V8.Task");
+  TRACE_EVENT_CALL_STATS_SCOPED(isolate(), "v8", "V8.Task");
   Heap* heap = isolate()->heap();
   double deadline_in_ms =
       deadline_in_seconds *