Clean up warnings.

sdk/lib/_internal/compiler/implementation/js_backend/minify_namer.dart

 // Copyright (c) 2011, 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 js_backend;
+
 /**
  * Assigns JavaScript identifiers to Dart variables, class-names and members.
  */
 class MinifyNamer extends Namer {
   MinifyNamer(Compiler compiler) : super(compiler);
 
   String get ISOLATE => 'I';
   String get ISOLATE_PROPERTIES => 'p';
   bool get shouldMinify => true;
 
@@ skipping 82 matching lines @@
   }
 
   int _alphaNumericNumber(int x) {
     if (x >= ALPHANUMERIC_CHARACTERS) x %= ALPHANUMERIC_CHARACTERS;
     if (x < 26) return $a + x;
     if (x < 52) return $A + x - 26;
     return $0 + x - 52;
   }
 
 }