heap: Move call to ThreadHeap::FlushV8References

We called Heap().FlushV8References in IncrementalMarkingStep after
returning from MarkPhaseAdvanceMarking. This means that
FlushV8References is not called during the atomic pause (which
doesn't use IncrementalMarkingStep). This could lead to errors.
Moving the call to FlushV8References into MarkPhaseAdvanceMarking
means it will be called regardless of whether we're in incremental
marking or atomic pause.

Bug: 986235
Change-Id: I70f85908f0ed8d750456f19d83f779734a5fac21
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1813328
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#702786}

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

@@ -324,7 +324,7 @@ bool ThreadHeap::AdvanceMarking(MarkingVisitor* visitor,
           },
           WorklistTaskId::MutatorThread);
       if (!finished)
-        return false;
+        break;
 
       // Iteratively mark all objects that were previously discovered while
       // being in construction. The objects can be processed incrementally once
@@ -336,7 +336,7 @@ bool ThreadHeap::AdvanceMarking(MarkingVisitor* visitor,
           },
           WorklistTaskId::MutatorThread);
       if (!finished)
-        return false;
+        break;
     }
 
     InvokeEphemeronCallbacks(visitor);
@@ -344,7 +344,9 @@ bool ThreadHeap::AdvanceMarking(MarkingVisitor* visitor,
     // Rerun loop if ephemeron processing queued more objects for tracing.
   } while (!marking_worklist_->IsGlobalEmpty());
 
-  return true;
+  FlushV8References();
+
+  return finished;
 }
 
 bool ThreadHeap::AdvanceConcurrentMarking(ConcurrentMarkingVisitor* visitor,

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

@@ -672,8 +672,6 @@ void ThreadState::AtomicPauseMarkPrologue(BlinkGC::StackState stack_state,
       // Stop concurrent markers
       marker_scheduler_->CancelAndWait();
       active_markers_ = 0;
-      // Flush the last remaining references concurrent markers found.
-      Heap().FlushV8References();
     }
     DisableIncrementalMarkingBarrier();
     current_gc_data_.reason = reason;
@@ -1111,8 +1109,6 @@ void ThreadState::IncrementalMarkingStep(BlinkGC::StackState stack_state) {
   bool complete = MarkPhaseAdvanceMarking(
       base::TimeTicks::Now() + next_incremental_marking_step_duration_);
 
-  Heap().FlushV8References();
-
   if (base::FeatureList::IsEnabled(
           blink::features::kBlinkHeapConcurrentMarking)) {
     complete = complete && ConcurrentMarkingStep();