Refactor VMTagScope to Thread* rather than Isolate*.

runtime/vm/tags.h

 // 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.
 
 #ifndef VM_TAGS_H_
 #define VM_TAGS_H_
 
 #include "vm/allocation.h"
 
 namespace dart {
@@ skipping 61 matching lines @@
   struct TagEntry {
     const char* name;
     uword id;
   };
   static TagEntry entries_[];
 };
 
 
 class VMTagScope : StackResource {
  public:
-  VMTagScope(Isolate* isolate, uword tag, bool conditional_set = true);
+  VMTagScope(Thread* thread, uword tag, bool conditional_set = true);
   ~VMTagScope();
  private:
   uword previous_tag_;
 
   DISALLOW_ALLOCATION();
   DISALLOW_IMPLICIT_CONSTRUCTORS(VMTagScope);
 };
 
 
 class VMTagCounters {
@@ skipping 21 matching lines @@
   static bool IsUserTag(uword tag_id) {
     return (tag_id >= kUserTagIdOffset) &&
            (tag_id < kUserTagIdOffset + kMaxUserTags);
   }
 };
 
 
 }  // namespace dart
 
 #endif  // VM_TAGS_H_