cppgc: Add missing top level scope

Marking on allocation was missing the top level scope.
Also adding a dedicated scope for on allocation to more clearly
distinguish it in traces.

Bug: chromium:1056170
Change-Id: I1b7d80c9f171f81988826de0174ef5b00d6f1d34
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2891572
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Auto-Submit: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74520}

src/heap/cppgc/marker.cc

@@ -377,6 +377,10 @@ bool MarkerBase::IncrementalMarkingStep(MarkingConfig::StackState stack_state) {
 }
 
 void MarkerBase::AdvanceMarkingOnAllocation() {
+  StatsCollector::EnabledScope stats_scope(heap().stats_collector(),
+                                           StatsCollector::kIncrementalMark);
+  StatsCollector::EnabledScope nested_scope(heap().stats_collector(),
+                                            StatsCollector::kMarkOnAllocation);
   if (AdvanceMarkingWithLimits()) {
     // Schedule another incremental task for finalizing without a stack.
     ScheduleIncrementalMarkingTask();

src/heap/cppgc/stats-collector.h

@@ -39,6 +39,7 @@ namespace internal {
   V(MarkTransitiveClosure)                  \
   V(MarkTransitiveClosureWithDeadline)      \
   V(MarkFlushEphemerons)                    \
+  V(MarkOnAllocation)                       \
   V(MarkProcessBailOutObjects)              \
   V(MarkProcessMarkingWorklist)             \
   V(MarkProcessWriteBarrierWorklist)        \