heap: Fix some statistics scopes

Some of the scopes were not reporting any data to GC metrics.
This CL replaces Scope with EnabledScope to fix these issues.

Bug: 986235
Change-Id: I21a8884faa491aa21b8d6a88e716c870f911da1f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1995320Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#730177}

third_party/blink/renderer/platform/heap/heap_page.cc

@@ -268,7 +268,7 @@ Address BaseArena::LazySweep(size_t allocation_size, size_t gc_info_index) {
   if (GetThreadState()->SweepForbidden())
     return nullptr;
 
-  ThreadHeapStatsCollector::Scope stats_scope(
+  ThreadHeapStatsCollector::EnabledScope stats_scope(
       GetThreadState()->Heap().stats_collector(),
       ThreadHeapStatsCollector::kLazySweepOnAllocation);
   ThreadState::SweepForbiddenScope sweep_forbidden(GetThreadState());

third_party/blink/renderer/platform/heap/thread_state.cc

@@ -1620,7 +1620,7 @@ void ThreadState::MarkPhasePrologue(BlinkGC::CollectionType collection_type,
 }
 
 void ThreadState::MarkPhaseVisitRoots() {
-  ThreadHeapStatsCollector::Scope stats_scope(
+  ThreadHeapStatsCollector::EnabledScope stats_scope(
       Heap().stats_collector(), ThreadHeapStatsCollector::kVisitRoots);
 
   Visitor* visitor = current_gc_data_.visitor.get();

third_party/blink/renderer/platform/heap/unified_heap_controller.cc

@@ -124,7 +124,7 @@ bool UnifiedHeapController::AdvanceTracing(double deadline_in_ms) {
   ThreadHeapStatsCollector::BlinkGCInV8Scope nested_scope(
       thread_state_->Heap().stats_collector());
   if (!thread_state_->in_atomic_pause()) {
-    ThreadHeapStatsCollector::Scope advance_tracing_scope(
+    ThreadHeapStatsCollector::EnabledScope advance_tracing_scope(
         thread_state_->Heap().stats_collector(),
         ThreadHeapStatsCollector::kUnifiedMarkingStep);
     // V8 calls into embedder tracing from its own marking to ensure