Revert "Rename internal library dart:_collection-dev to dart:_internal."

sdk/lib/internal/symbol.dart

 // 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.
 
-part of dart._collection.dev;
+part of dart._internal;
 
 /**
  * Implementation of [core.Symbol].  This class uses the same name as
  * a core class so a user can't tell the difference.
  *
  * The purpose of this class is to hide [_name] from user code, but
  * make it accessible to Dart platform code via the static method
  * [getName].
  */
 class Symbol implements core.Symbol {
@@ skipping 52 matching lines @@
     if (name.startsWith('_')) {
       throw new ArgumentError('"$name" is a private identifier');
     }
     if (!validationPattern.hasMatch(name)) {
       throw new ArgumentError(
           '"$name" is not an identifier or an empty String');
     }
     return name;
   }
 }