[heap] Restore TSAN exception for page flags (the second try).

This is a follow-up for 8ed81dde.

The TSAN exception has to be in MarkObject because that is called from
two places in concurrent marking.

Bug: v8:7574
Change-Id: If36b564bce0970c9b44c029055114bb6e2a74059
Reviewed-on: https://chromium-review.googlesource.com/973526
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52157}

src/heap/concurrent-marking.cc

@@ -93,13 +93,6 @@ class ConcurrentMarkingVisitor final
 
   void ProcessStrongHeapObject(HeapObject* host, Object** slot,
                                HeapObject* heap_object) {
-#ifdef THREAD_SANITIZER
-    // Perform a dummy acquire load to tell TSAN that there is no data race
-    // in mark-bit initialization. See MemoryChunk::Initialize for the
-    // corresponding release store.
-    MemoryChunk* chunk = MemoryChunk::FromAddress(heap_object->address());
-    CHECK_NOT_NULL(chunk->synchronized_heap());
-#endif
     MarkObject(heap_object);
     MarkCompactCollector::RecordSlot(host, slot, heap_object);
   }
@@ -364,6 +357,13 @@ class ConcurrentMarkingVisitor final
   }
 
   void MarkObject(HeapObject* object) {
+#ifdef THREAD_SANITIZER
+    // Perform a dummy acquire load to tell TSAN that there is no data race
+    // in mark-bit initialization. See MemoryChunk::Initialize for the
+    // corresponding release store.
+    MemoryChunk* chunk = MemoryChunk::FromAddress(object->address());
+    CHECK_NOT_NULL(chunk->synchronized_heap());
+#endif
     if (marking_state_.WhiteToGrey(object)) {
       shared_.Push(object);
     }