Filter out invalid slots in store buffer eagerly during object transition.

src/heap/store-buffer.h

Index: src/heap/store-buffer.h
diff --git a/src/heap/store-buffer.h b/src/heap/store-buffer.h
index 9670f62a8a9a1d55a96c374cab1ba7660710d5c2..cbeaec20a3e68d3460615d71ac938140158921fa 100644
--- a/src/heap/store-buffer.h
+++ b/src/heap/store-buffer.h
@@ -36,6 +36,10 @@ class StoreBuffer {
   // This is used to add addresses to the store buffer non-concurrently.
   inline void Mark(Address addr);
 
+  // Removes the given slot from the store buffer non-concurrently. If the
+  // slot was never added to the store buffer, then the function does nothing.
+  void Remove(Address addr);
+
   // Slots that do not point to the ToSpace after callback invocation will be
   // removed from the set.
   void IteratePointersToNewSpace(ObjectSlotCallback callback);