Change imports to clean up irritating warning

sdk/lib/svg/dart2js/svg_dart2js.dart

 /**
  * Scalable Vector Graphics:
  * Two-dimensional vector graphics with support for events and animation.
  *
  * For details about the features and syntax of SVG, a W3C standard,
  * refer to the
  * [Scalable Vector Graphics Specification](http://www.w3.org/TR/SVG/).
  */
 library dart.dom.svg;
 
 import 'dart:async';
 import 'dart:collection';
-import 'dart:_internal';
+import 'dart:_internal' show FixedLengthListMixin;
 import 'dart:html';
 import 'dart:html_common';
 import 'dart:_js_helper' show Creates, Returns, JSName, Native;
 import 'dart:_foreign_helper' show JS;
 import 'dart:_interceptors' show Interceptor;
 // DO NOT EDIT - unless you are editing documentation as per:
 // https://code.google.com/p/dart/wiki/ContributingHTMLDocumentation
 // Auto-generated dart:svg library.
 
 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
@@ skipping 5938 matching lines @@
   /**
    * Constructor instantiated by the DOM when a custom element has been created.
    *
    * This can only be called by subclasses from their created constructor.
    */
   _SVGMPathElement.created() : super.created();
 
   // From SVGURIReference
 
 }