Use NeedsContext() instead of comparing num_heap_slots().

src/crankshaft/x64/lithium-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/crankshaft/x64/lithium-x64.h"
 
 #include <sstream>
 
 #if V8_TARGET_ARCH_X64
 
@@ skipping 889 matching lines @@
 }
 
 
 LInstruction* LChunkBuilder::DoGoto(HGoto* instr) {
   return new(zone()) LGoto(instr->FirstSuccessor());
 }
 
 
 LInstruction* LChunkBuilder::DoPrologue(HPrologue* instr) {
   LInstruction* result = new (zone()) LPrologue();
-  if (info_->scope()->num_heap_slots() > 0) {
+  if (info_->scope()->NeedsContext()) {
     result = MarkAsCall(result, instr);
   }
   return result;
 }
 
 
 LInstruction* LChunkBuilder::DoDebugBreak(HDebugBreak* instr) {
   return new(zone()) LDebugBreak();
 }
 
@@ skipping 1648 matching lines @@
   LOperand* index = UseTempRegister(instr->index());
   LLoadFieldByIndex* load = new(zone()) LLoadFieldByIndex(object, index);
   LInstruction* result = DefineSameAsFirst(load);
   return AssignPointerMap(result);
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64