Reland r19897 "Fix memory leak caused by treating Code::next_code_link as strong in marker.

src/heap.cc

Index: src/heap.cc
diff --git a/src/heap.cc b/src/heap.cc
index eae7241cf1782dc59d175d36c0b35830725771b6..2e67e23741af7c9eab6130ba32a7b75cb20b7eb9 100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -1775,6 +1775,18 @@ static Object* VisitWeakList(Heap* heap,
 }
 
 
+template <class T>
+static void ClearWeakList(Heap* heap,
+                          Object* list) {
+  Object* undefined = heap->undefined_value();
+  while (list != undefined) {
+    T* candidate = reinterpret_cast<T*>(list);
+    list = WeakListVisitor<T>::WeakNext(candidate);
+    WeakListVisitor<T>::SetWeakNext(candidate, undefined);
+  }
+}
+
+
 template<>
 struct WeakListVisitor<JSFunction> {
   static void SetWeakNext(JSFunction* function, Object* next) {
@@ -1868,7 +1880,11 @@ struct WeakListVisitor<Context> {
     }
   }
 
-  static void VisitPhantomObject(Heap*, Context*) {
+  static void VisitPhantomObject(Heap* heap, Context* context) {
+    ClearWeakList<JSFunction>(heap,
+        context->get(Context::OPTIMIZED_FUNCTIONS_LIST));
+    ClearWeakList<Code>(heap, context->get(Context::OPTIMIZED_CODE_LIST));
+    ClearWeakList<Code>(heap, context->get(Context::DEOPTIMIZED_CODE_LIST));
   }
 
   static int WeakNextOffset() {
@@ -4126,6 +4142,7 @@ MaybeObject* Heap::CreateCode(const CodeDesc& desc,
   code->set_is_crankshafted(crankshafted);
   code->set_deoptimization_data(empty_fixed_array(), SKIP_WRITE_BARRIER);
   code->set_raw_type_feedback_info(undefined_value());
+  code->set_next_code_link(undefined_value());
   code->set_handler_table(empty_fixed_array(), SKIP_WRITE_BARRIER);
   code->set_gc_metadata(Smi::FromInt(0));
   code->set_ic_age(global_ic_age_);