Renames the isolate's mutator_thread_ to scheduled_mutator_thread_

runtime/vm/base_isolate.h

Index: runtime/vm/base_isolate.h
diff --git a/runtime/vm/base_isolate.h b/runtime/vm/base_isolate.h
index 544988095f8ed7d6e156d895334451624ae06601..58a0cbbb8e12a8b49211f98d5cc133fde2b9dd70 100644
--- a/runtime/vm/base_isolate.h
+++ b/runtime/vm/base_isolate.h
@@ -31,13 +31,13 @@ class BaseIsolate {
 #endif
 
  protected:
-  BaseIsolate() : mutator_thread_(NULL) {}
+  BaseIsolate() : scheduled_mutator_thread_(NULL) {}
 
   ~BaseIsolate() {
     // Do not delete stack resources: top_resource_ and current_zone_.
   }
 
-  Thread* mutator_thread_;
+  Thread* scheduled_mutator_thread_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(BaseIsolate);