Use Unique<Cell> and Unique<PropertyCell> in LoadGlobalCell and StoreGlobalCell.

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index 04ae3910609840a761db19435374e2431244958b..83a8cb249841051b0a1ac62d50d59be5085823f6 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -2668,7 +2668,7 @@ void LCodeGen::DoReturn(LReturn* instr) {
 
 void LCodeGen::DoLoadGlobalCell(LLoadGlobalCell* instr) {
   Register result = ToRegister(instr->result());
-  __ LoadGlobalCell(result, instr->hydrogen()->cell());
+  __ LoadGlobalCell(result, instr->hydrogen()->cell().handle());
   if (instr->hydrogen()->RequiresHoleCheck()) {
     __ CompareRoot(result, Heap::kTheHoleValueRootIndex);
     DeoptimizeIf(equal, instr->environment());
@@ -2690,7 +2690,7 @@ void LCodeGen::DoLoadGlobalGeneric(LLoadGlobalGeneric* instr) {
 
 void LCodeGen::DoStoreGlobalCell(LStoreGlobalCell* instr) {
   Register value = ToRegister(instr->value());
-  Handle<Cell> cell_handle = instr->hydrogen()->cell();
+  Handle<Cell> cell_handle = instr->hydrogen()->cell().handle();
 
   // If the cell we are storing to contains the hole it could have
   // been deleted from the property dictionary. In that case, we need