Enable weak embedded objects in optimized code with a fix for heap verifier.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 4d8a45bb2d58d3066219dfc01d80b03ea64af9c9..e0ab9841cb29e59a00091ae1d02cd0c51632238b 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -4001,6 +4001,15 @@ class WeakHashTable: public HashTable<WeakHashTableShape<2>, Object*> {
   // key to the hole value causes removal of the whole entry.
   MUST_USE_RESULT MaybeObject* Put(Object* key, Object* value);
 
+  // This function is called when heap verification is turned on.
+  void Zap(Object* value) {
+    int capacity = Capacity();
+    for (int i = 0; i < capacity; i++) {
+      set(EntryToIndex(i), value);
+      set(EntryToValueIndex(i), value);
+    }
+  }
+
  private:
   friend class MarkCompactCollector;