Migrate most uses of Isolate::current_zone to Thread::zone.

runtime/vm/deopt_instructions.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/deopt_instructions.h"
 
 #include "vm/assembler.h"
 #include "vm/code_patcher.h"
 #include "vm/compiler.h"
 #include "vm/intermediate_language.h"
@@ skipping 1173 matching lines @@
       return i;
     }
   }
   return -1;
 }
 
 
 static uint8_t* ZoneReAlloc(uint8_t* ptr,
                             intptr_t old_size,
                             intptr_t new_size) {
-  return Isolate::Current()->current_zone()->Realloc<uint8_t>(
+  return Thread::Current()->zone()->Realloc<uint8_t>(
       ptr, old_size, new_size);
 }
 
 
 RawTypedData* DeoptInfoBuilder::CreateDeoptInfo(const Array& deopt_table) {
   intptr_t length = instructions_.length();
 
   // Count the number of instructions that are a shared suffix of some deopt
   // info already written.
   TrieNode* suffix = trie_root_;
@@ skipping 89 matching lines @@
                           Smi* offset,
                           TypedData* info,
                           Smi* reason) {
   intptr_t i = index * kEntrySize;
   *offset ^= table.At(i);
   *info ^= table.At(i + 1);
   *reason ^= table.At(i + 2);
 }
 
 }  // namespace dart