Use weak cells in dependent code.

src/lithium.cc

Index: src/lithium.cc
diff --git a/src/lithium.cc b/src/lithium.cc
index 43d690c0c74c827225ffd711970603d4f5ea538d..cd072acb561ba21bbc201dbfabb3ca498da2abff 100644
--- a/src/lithium.cc
+++ b/src/lithium.cc
@@ -416,10 +416,11 @@ Representation LChunk::LookupLiteralRepresentation(
 static void AddWeakObjectToCodeDependency(Isolate* isolate,
                                           Handle<Object> object,
                                           Handle<Code> code) {
+  Handle<WeakCell> cell = Code::WeakCellFor(code);
   Heap* heap = isolate->heap();
   heap->EnsureWeakObjectToCodeTable();
   Handle<DependentCode> dep(heap->LookupWeakObjectToCodeDependency(object));
-  dep = DependentCode::Insert(dep, DependentCode::kWeakCodeGroup, code);
+  dep = DependentCode::InsertWeakCode(dep, DependentCode::kWeakCodeGroup, cell);
   heap->AddWeakObjectToCodeDependency(object, dep);
 }
 
@@ -469,6 +470,9 @@ void LChunk::RegisterWeakObjectsInOptimizedCode(Handle<Code> code) const {
 
 
 void LChunk::CommitDependencies(Handle<Code> code) const {
+  if (!code->is_optimized_code()) return;
+  HandleScope scope(isolate());
+
   for (MapSet::const_iterator it = deprecation_dependencies_.begin(),
        iend = deprecation_dependencies_.end(); it != iend; ++it) {
     Handle<Map> map = *it;
@@ -486,7 +490,7 @@ void LChunk::CommitDependencies(Handle<Code> code) const {
   }
 
   info_->CommitDependencies(code);
-  if (code->is_optimized_code()) RegisterWeakObjectsInOptimizedCode(code);
+  RegisterWeakObjectsInOptimizedCode(code);
 }