Link all global contexts into a weak list.

src/serialize.cc

Index: src/serialize.cc
diff --git a/src/serialize.cc b/src/serialize.cc
index cde7577c7a542811ee61a7b3a15f9a32cd5699fe..ccba737d15908980fe9d1cdf7a8f425ae0b4be50 100644
--- a/src/serialize.cc
+++ b/src/serialize.cc
@@ -500,7 +500,7 @@ void ExternalReferenceEncoder::Put(Address key, int index) {
 
 
 ExternalReferenceDecoder::ExternalReferenceDecoder()
-  : encodings_(NewArray<Address*>(kTypeCodeCount)) {
+    : encodings_(NewArray<Address*>(kTypeCodeCount)) {
   ExternalReferenceTable* external_references =
       ExternalReferenceTable::instance();
   for (int type = kFirstTypeCode; type < kTypeCodeCount; ++type) {
@@ -619,6 +619,8 @@ void Deserializer::Deserialize() {
   external_reference_decoder_ = new ExternalReferenceDecoder();
   Heap::IterateStrongRoots(this, VISIT_ONLY_STRONG);
   Heap::IterateWeakRoots(this, VISIT_ALL);
+
+  Heap::set_global_contexts_list(Heap::undefined_value());
 }