Add IsMutatorThread to the Thread class and use it instead of MutatorThreadIsCurrentThread

runtime/vm/isolate.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_ISOLATE_H_
 #define VM_ISOLATE_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/atomic.h"
@@ skipping 133 matching lines @@
   void set_message_notify_callback(Dart_MessageNotifyCallback value) {
     message_notify_callback_ = value;
   }
 
   // Limited public access to BaseIsolate::mutator_thread_ for code that
   // must treat the mutator as the default or a special case. Prefer code
   // that works uniformly across all threads.
   bool HasMutatorThread() {
     return mutator_thread_ != NULL;
   }
-  bool MutatorThreadIsCurrentThread() {
-    return mutator_thread_ == Thread::Current();
+  Thread* mutator_thread() const {
+    return mutator_thread_;
   }
 
   const char* name() const { return name_; }
   const char* debugger_name() const { return debugger_name_; }
   void set_debugger_name(const char* name);
 
   int64_t start_time() const { return start_time_; }
 
   Dart_Port main_port() const { return main_port_; }
   void set_main_port(Dart_Port port) {
@@ skipping 859 matching lines @@
   uint8_t* serialized_message_;
   intptr_t serialized_message_len_;
   Isolate::Flags isolate_flags_;
   bool paused_;
   bool errors_are_fatal_;
 };
 
 }  // namespace dart
 
 #endif  // VM_ISOLATE_H_