Remove the dependency of Zone on Isolate

src/compiler/jump-threading.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/jump-threading.h"
 #include "src/compiler/code-generator-impl.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
@@ skipping 122 matching lines @@
   }
 
   return state.forwarded;
 }
 
 
 void JumpThreading::ApplyForwarding(ZoneVector<RpoNumber>& result,
                                     InstructionSequence* code) {
   if (!FLAG_turbo_jt) return;
 
-  Zone local_zone(code->zone()->isolate());
+  Zone local_zone;
   ZoneVector<bool> skip(static_cast<int>(result.size()), false, &local_zone);
 
   // Skip empty blocks when the previous block doesn't fall through.
   bool prev_fallthru = true;
   for (auto const block : code->instruction_blocks()) {
     int block_num = block->rpo_number().ToInt();
     skip[block_num] = !prev_fallthru && result[block_num].ToInt() != block_num;
 
     bool fallthru = true;
     for (int i = block->code_start(); i < block->code_end(); ++i) {
@@ skipping 35 matching lines @@
     if (block->IsDeferred()) {
       block->set_ao_number(RpoNumber::FromInt(ao));
       if (!skip[block->rpo_number().ToInt()]) ao++;
     }
   }
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8