Get rid of deprecated methods accessing mutator_thread_ instead of current thread

runtime/vm/object_graph.h

 // Copyright (c) 2014, 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_OBJECT_GRAPH_H_
 #define VM_OBJECT_GRAPH_H_
 
 #include "vm/allocation.h"
 #include "vm/object.h"
 
@@ skipping 35 matching lines @@
       kBacktrack,  // Ignore this object's pointers.
       kAbort,      // Terminate the entire search immediately.
     };
     virtual ~Visitor() { }
     // Visits the object pointed to by *it. The iterator is only valid
     // during this call. This method must not allocate from the heap or
     // trigger GC in any way.
     virtual Direction VisitObject(StackIterator* it) = 0;
   };
 
-  explicit ObjectGraph(Isolate* isolate);
+  explicit ObjectGraph(Thread* thread);
   ~ObjectGraph();
 
   // Visits all strongly reachable objects in the isolate's heap, in a
   // pre-order, depth first traversal.
   void IterateObjects(Visitor* visitor);
 
   // Like 'IterateObjects', but restricted to objects reachable from 'root'
   // (including 'root' itself).
   void IterateObjectsFrom(const Object& root, Visitor* visitor);
 
@@ skipping 27 matching lines @@
   // TODO(koda): Document format; support streaming/chunking.
   intptr_t Serialize(WriteStream* stream);
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(ObjectGraph);
 };
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_GRAPH_H_