Remove the dependency of Zone on Isolate

src/compiler/graph-inl.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_GRAPH_INL_H_
 #define V8_COMPILER_GRAPH_INL_H_
 
 #include "src/compiler/generic-algorithm.h"
 #include "src/compiler/graph.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
 template <class Visitor>
 void Graph::VisitNodeInputsFromEnd(Visitor* visitor) {
-  Zone tmp_zone(zone()->isolate());
+  Zone tmp_zone;
   GenericGraphVisit::Visit<Visitor>(this, &tmp_zone, end(), visitor);
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_GRAPH_INL_H_