Fix clang build; remove dead private field.

src/compiler/scheduler.h

 // Copyright 2013 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.
 
 #ifndef V8_COMPILER_SCHEDULER_H_
 #define V8_COMPILER_SCHEDULER_H_
 
 #include <vector>
 
 #include "src/v8.h"
@@ skipping 11 matching lines @@
 // ordering the basic blocks in the special RPO order.
 class Scheduler {
  public:
   // Create a new schedule and place all computations from the graph in it.
   static Schedule* ComputeSchedule(Graph* graph);
 
   // Compute the RPO of blocks in an existing schedule.
   static BasicBlockVector* ComputeSpecialRPO(Schedule* schedule);
 
  private:
-  Zone* zone_;
   Graph* graph_;
   Schedule* schedule_;
   NodeVector branches_;
   NodeVector calls_;
   NodeVector deopts_;
   NodeVector returns_;
   NodeVector loops_and_merges_;
   BasicBlockVector node_block_placement_;
   IntVector unscheduled_uses_;
   NodeVectorVector scheduled_nodes_;
@@ skipping 33 matching lines @@
   void PrepareUses();
 
   friend class ScheduleLateNodeVisitor;
   void ScheduleLate();
 };
 }
 }
 }  // namespace v8::internal::compiler
 
 #endif  // V8_COMPILER_SCHEDULER_H_