Remove the dependency of Zone on Isolate

src/compiler/control-reducer.cc

 // Copyright 2014 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/compiler/common-operator.h"
 #include "src/compiler/control-reducer.h"
 #include "src/compiler/graph.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/node-marker.h"
 #include "src/compiler/node-matchers.h"
@@ skipping 545 matching lines @@
 
 void ControlReducer::TrimGraph(Zone* zone, JSGraph* jsgraph) {
   ControlReducerImpl impl(zone, jsgraph, NULL);
   impl.Trim();
 }
 
 
 Node* ControlReducer::ReducePhiForTesting(JSGraph* jsgraph,
                                           CommonOperatorBuilder* common,
                                           Node* node) {
-  Zone zone(jsgraph->graph()->zone()->isolate());
+  Zone zone;
   ControlReducerImpl impl(&zone, jsgraph, common);
   return impl.ReducePhi(node);
 }
 
 
 Node* ControlReducer::ReduceMergeForTesting(JSGraph* jsgraph,
                                             CommonOperatorBuilder* common,
                                             Node* node) {
-  Zone zone(jsgraph->graph()->zone()->isolate());
+  Zone zone;
   ControlReducerImpl impl(&zone, jsgraph, common);
   return impl.ReduceMerge(node);
 }
 
 
 Node* ControlReducer::ReduceBranchForTesting(JSGraph* jsgraph,
                                              CommonOperatorBuilder* common,
                                              Node* node) {
-  Zone zone(jsgraph->graph()->zone()->isolate());
+  Zone zone;
   ControlReducerImpl impl(&zone, jsgraph, common);
   return impl.ReduceBranch(node);
 }
 }
 }
 }  // namespace v8::internal::compiler