Address review comments from a previous CL.

vm/heap_profiler.cc

 // Copyright (c) 2012, 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/heap_profiler.h"
 
 #include "vm/dart_api_state.h"
 #include "vm/object.h"
 #include "vm/raw_object.h"
 #include "vm/stack_frame.h"
@@ skipping 395 matching lines @@
 //   ID - class name string ID
 void HeapProfiler::WriteLoadClass(const RawClass* raw_class) {
   Record record(kLoadClass, this);
   // class serial number (always > 0)
   record.Write32(1);
   // class object ID
   record.WritePointer(raw_class);
   // stack trace serial number
   record.Write32(0);
   if (raw_class->ptr()->name_ == String::null()) {
-    intptr_t class_index = Object::GetSingletonClassIndex(raw_class);
-    const char* name = Object::GetSingletonClassName(class_index);
+    const char* name = Object::GetSingletonClassName(raw_class->id_);
     record.WritePointer(StringId(name));
   } else {
     record.WritePointer(StringId(raw_class->ptr()->name_));
   }
 }
 
 
 // STACK TRACE - 0x05
 //
 //  u4 - stack trace serial number
@@ skipping 292 matching lines @@
   RawObject* raw_obj = handle->raw();
   visitor_->VisitPointer(&raw_obj);
 }
 
 
 void HeapProfilerObjectVisitor::VisitObject(RawObject* raw_obj) {
   profiler_->WriteObject(raw_obj);
 }
 
 }  // namespace dart