Synchronize on concurrent store buffer entries.

src/heap/store-buffer-inl.h

Index: src/heap/store-buffer-inl.h
diff --git a/src/heap/store-buffer-inl.h b/src/heap/store-buffer-inl.h
index 230384af7a34f74ce42281308512b74af0df68e7..1f3dda21d223788360acddf44399548ea97bfe09 100644
--- a/src/heap/store-buffer-inl.h
+++ b/src/heap/store-buffer-inl.h
@@ -26,6 +26,12 @@ void StoreBuffer::Mark(Address addr) {
 }
 
 
+inline void StoreBuffer::MarkSynchronized(Address addr) {
+  base::LockGuard<base::Mutex> lock_guard(&mutex_);
+  Mark(addr);
+}
+
+
 void StoreBuffer::EnterDirectlyIntoStoreBuffer(Address addr) {
   if (store_buffer_rebuilding_enabled_) {
     SLOW_DCHECK(!heap_->code_space()->Contains(addr) &&