Use a WeakCell in the CallIC type vector.

src/code-stubs-hydrogen.cc

Index: src/code-stubs-hydrogen.cc
diff --git a/src/code-stubs-hydrogen.cc b/src/code-stubs-hydrogen.cc
index 83a994b1c31c5c16f68854f01016b2923b586dc9..d971c3c84050d2e4568862740ea0eba1ed19defb 100644
--- a/src/code-stubs-hydrogen.cc
+++ b/src/code-stubs-hydrogen.cc
@@ -450,6 +450,10 @@ Handle<Code> FastCloneShallowObjectStub::GenerateCode() {
 
 template <>
 HValue* CodeStubGraphBuilder<CreateAllocationSiteStub>::BuildCodeStub() {
+  // This stub is performance sensitive, the generated code must be tuned
+  // so that it doesn't build an eager frame.
+  info()->MarkMustNotHaveEagerFrame();
+
   HValue* size = Add<HConstant>(AllocationSite::kSize);
   HInstruction* object = Add<HAllocate>(size, HType::JSObject(), TENURED,
       JS_OBJECT_TYPE);
@@ -523,6 +527,36 @@ Handle<Code> CreateAllocationSiteStub::GenerateCode() {
 
 
 template <>
+HValue* CodeStubGraphBuilder<CreateWeakCellStub>::BuildCodeStub() {
+  // This stub is performance sensitive, the generated code must be tuned
+  // so that it doesn't build an eager frame.
+  info()->MarkMustNotHaveEagerFrame();
+
+  HValue* size = Add<HConstant>(WeakCell::kSize);
+  HInstruction* object =
+      Add<HAllocate>(size, HType::JSObject(), TENURED, JS_OBJECT_TYPE);
+
+  Handle<Map> weak_cell_map = isolate()->factory()->weak_cell_map();
+  AddStoreMapConstant(object, weak_cell_map);
+
+  HInstruction* value = GetParameter(CreateWeakCellDescriptor::kValueIndex);
+  Add<HStoreNamedField>(object, HObjectAccess::ForWeakCellValue(), value);
+  Add<HStoreNamedField>(object, HObjectAccess::ForWeakCellNext(),
+                        graph()->GetConstantUndefined());
+
+  HInstruction* feedback_vector =
+      GetParameter(CreateWeakCellDescriptor::kVectorIndex);
+  HInstruction* slot = GetParameter(CreateWeakCellDescriptor::kSlotIndex);
+  Add<HStoreKeyed>(feedback_vector, slot, object, FAST_ELEMENTS,
+                   INITIALIZING_STORE);
+  return graph()->GetConstant0();
+}
+
+
+Handle<Code> CreateWeakCellStub::GenerateCode() { return DoGenerateCode(this); }
+
+
+template <>
 HValue* CodeStubGraphBuilder<LoadScriptContextFieldStub>::BuildCodeStub() {
   int context_index = casted_stub()->context_index();
   int slot_index = casted_stub()->slot_index();