Fix Win64 after r24758.

BUG=
TBR=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/663343002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24759 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/objects-inl.h

@@ -1930,9 +1930,7 @@ void PropertyCell::set_type_raw(Object* val, WriteBarrierMode ignored) {
 }
 
 
-Object* WeakCell::value() const {
-  return HeapObject::cast(READ_FIELD(this, kValueOffset));
-}
+Object* WeakCell::value() const { return READ_FIELD(this, kValueOffset); }
 
 
 void WeakCell::clear() {