[heap] Report proper GC type in prologue/eplilogue callbacks.

Followup to https://codereview.chromium.org/1288683005

BUG=chromium:521946
LOG=N

Review URL: https://codereview.chromium.org/1313023002

Cr-Commit-Position: refs/heads/master@{#30345}

src/heap/heap.cc

@@ -768,9 +768,7 @@ void Heap::OverApproximateWeakClosure(const char* gc_reason) {
       GCTracer::Scope scope(tracer(), GCTracer::Scope::EXTERNAL);
       VMState<EXTERNAL> state(isolate_);
       HandleScope handle_scope(isolate_);
-      // TODO(mlippautz): Report kGCTypeIncremental once blink updates its
-      // filtering.
-      CallGCPrologueCallbacks(kGCTypeMarkSweepCompact, kNoGCCallbackFlags);
+      CallGCPrologueCallbacks(kGCTypeIncrementalMarking, kNoGCCallbackFlags);
     }
   }
   incremental_marking()->MarkObjectGroups();
@@ -781,9 +779,7 @@ void Heap::OverApproximateWeakClosure(const char* gc_reason) {
       GCTracer::Scope scope(tracer(), GCTracer::Scope::EXTERNAL);
       VMState<EXTERNAL> state(isolate_);
       HandleScope handle_scope(isolate_);
-      // TODO(mlippautz): Report kGCTypeIncremental once blink updates its
-      // filtering.
-      CallGCEpilogueCallbacks(kGCTypeMarkSweepCompact, kNoGCCallbackFlags);
+      CallGCEpilogueCallbacks(kGCTypeIncrementalMarking, kNoGCCallbackFlags);
     }
   }
 }