[heap] Add timer to incremental marking finalization phase.

src/heap/incremental-marking.cc

Index: src/heap/incremental-marking.cc
diff --git a/src/heap/incremental-marking.cc b/src/heap/incremental-marking.cc
index 494aa67f726fb67d0bca59f6137aaaf080d345b6..54c89acbd2272223aec4f9ee5f6396e0bfa90a98 100644
--- a/src/heap/incremental-marking.cc
+++ b/src/heap/incremental-marking.cc
@@ -652,6 +652,8 @@ void IncrementalMarking::FinalizeIncrementally() {
   DCHECK(!finalize_marking_completed_);
   DCHECK(IsMarking());
 
+  double start = heap_->MonotonicallyIncreasingTimeInMs();
+
   int old_marking_deque_top =
       heap_->mark_compact_collector()->marking_deque()->top();
 
@@ -666,6 +668,18 @@ void IncrementalMarking::FinalizeIncrementally() {
       abs(old_marking_deque_top -
           heap_->mark_compact_collector()->marking_deque()->top());
 
+  double end = heap_->MonotonicallyIncreasingTimeInMs();
+  double delta = end - start;
+  heap_->tracer()->AddMarkingTime(delta);
+  heap_->tracer()->AddIncrementalMarkingFinalizationStep(delta);
+  if (FLAG_trace_incremental_marking) {
+    PrintF(
+        "[IncrementalMarking] Finalize incrementally round %d, "
+        "spent %d ms, marking progress %d.\n",
+        static_cast<int>(delta), incremental_marking_finalization_rounds_,
+        marking_progress);
+  }
+
   ++incremental_marking_finalization_rounds_;
   if ((incremental_marking_finalization_rounds_ >=
        FLAG_max_incremental_marking_finalization_rounds) ||