Remove redundant variable descriptors from optimized code.

runtime/vm/debugger.h

 // 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.
 
 #ifndef VM_DEBUGGER_H_
 #define VM_DEBUGGER_H_
 
 #include "include/dart_debugger_api.h"
 
 #include "vm/object.h"
 #include "vm/port.h"
 
 namespace dart {
 
-class ActiveVariables;
 class CodeBreakpoint;
 class Isolate;
 class JSONArray;
 class JSONStream;
 class ObjectPointerVisitor;
 class RemoteObjectCache;
 class SourceBreakpoint;
 class StackFrame;
 
 // SourceBreakpoint represents a user-specified breakpoint location in
@@ skipping 537 matching lines @@
 
   friend class Isolate;
   friend class SourceBreakpoint;
   DISALLOW_COPY_AND_ASSIGN(Debugger);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_DEBUGGER_H_