[turbofan] fix build after r24726

TBR=bmeurer@chromium.org

BUG=

Review URL: https://codereview.chromium.org/669643002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24727 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/compiler/instruction.cc

@@ -382,7 +382,7 @@ static void InitializeInstructionBlocks(Zone* zone, const Schedule* schedule,
 
 InstructionSequence::InstructionSequence(Linkage* linkage, const Graph* graph,
                                          const Schedule* schedule)
-    : zone_(graph->zone()->isolate()),
+    : zone_(schedule->zone()),
       node_count_(graph->NodeCount()),
       node_map_(zone()->NewArray<int>(node_count_)),
       instruction_blocks_(static_cast<int>(schedule->rpo_order()->size()), NULL,

src/compiler/instruction.h

@@ -905,10 +905,10 @@ class InstructionSequence FINAL {
   }
 
   Frame* frame() { return &frame_; }
-  Isolate* isolate() { return zone()->isolate(); }
+  Isolate* isolate() const { return zone()->isolate(); }
   Linkage* linkage() const { return linkage_; }
   const PointerMapDeque* pointer_maps() const { return &pointer_maps_; }
-  Zone* zone() { return &zone_; }
+  Zone* zone() const { return zone_; }
 
   // Used by the instruction selector while adding instructions.
   int AddInstruction(Instruction* instr);
@@ -962,7 +962,7 @@ class InstructionSequence FINAL {
 
   typedef std::set<int, std::less<int>, ZoneIntAllocator> VirtualRegisterSet;
 
-  Zone zone_;
+  Zone* zone_;
   int node_count_;
   int* node_map_;
   InstructionBlocks instruction_blocks_;