Temporarily move vm_tag_ from BaseIsolate to Isolate.

runtime/vm/isolate.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/isolate.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/json.h"
 #include "vm/code_observers.h"
@@ skipping 418 matching lines @@
 #define REUSABLE_HANDLE_SCOPE_INIT(object)                                     \
   reusable_##object##_handle_scope_active_(false),
 #else
 #define REUSABLE_HANDLE_SCOPE_INIT(object)
 #endif  // defined(DEBUG)
 
 #define REUSABLE_HANDLE_INITIALIZERS(object)                                   \
   object##_handle_(NULL),
 
 Isolate::Isolate()
-    : store_buffer_(),
+    : vm_tag_(0),
+      store_buffer_(),
       message_notify_callback_(NULL),
       name_(NULL),
       start_time_(OS::GetCurrentTimeMicros()),
       main_port_(0),
       origin_id_(0),
       pause_capability_(0),
       terminate_capability_(0),
       heap_(NULL),
       object_store_(NULL),
       top_exit_frame_info_(0),
@@ skipping 38 matching lines @@
       metrics_list_head_(NULL),
       next_(NULL),
       REUSABLE_HANDLE_LIST(REUSABLE_HANDLE_INITIALIZERS)
       REUSABLE_HANDLE_LIST(REUSABLE_HANDLE_SCOPE_INIT)
       reusable_handles_() {
   set_vm_tag(VMTag::kIdleTagId);
   set_user_tag(UserTags::kDefaultUserTag);
 }
 
 Isolate::Isolate(Isolate* original)
-    : store_buffer_(true),
+    : vm_tag_(0),
+      store_buffer_(true),
       class_table_(original->class_table()),
       message_notify_callback_(NULL),
       name_(NULL),
       start_time_(OS::GetCurrentTimeMicros()),
       main_port_(0),
       pause_capability_(0),
       terminate_capability_(0),
       heap_(NULL),
       object_store_(NULL),
       top_exit_frame_info_(0),
@@ skipping 1120 matching lines @@
                            serialized_message_, serialized_message_len_);
 }
 
 
 void IsolateSpawnState::Cleanup() {
   SwitchIsolateScope switch_scope(I);
   Dart::ShutdownIsolate();
 }
 
 }  // namespace dart