Move IterableMixinWorkaround to internal library.

sdk/lib/web_sql/dart2js/web_sql_dart2js.dart

 /**
  * An API for storing data in the browser that can be queried with SQL.
  *
  * **Caution:** this specification is no longer actively maintained by the Web
  * Applications Working Group and may be removed at any time.
  * See [the W3C Web SQL Database specification](http://www.w3.org/TR/webdatabase/)
  * for more information.
  *
  * The [dart:indexed_db] APIs is a recommended alternatives.
  */
 library dart.dom.web_sql;
 
 import 'dart:async';
 import 'dart:collection';
+import 'dart:_collection-dev';
 import 'dart:html';
 import 'dart:html_common';
 import 'dart:_js_helper' show convertDartClosureToJS, Creates, JavaScriptIndexingBehavior, JSName;
 import 'dart:_foreign_helper' show JS;
 // DO NOT EDIT - unless you are editing documentation as per:
 // https://code.google.com/p/dart/wiki/ContributingHTMLDocumentation
 // Auto-generated dart:audio library.
 
 
 
@@ skipping 414 matching lines @@
 // BSD-style license that can be found in the LICENSE file.
 
 
 @DocsEditable
 @DomName('SQLTransactionSync')
 @SupportedBrowser(SupportedBrowser.CHROME)
 @SupportedBrowser(SupportedBrowser.SAFARI)
 @Experimental
 abstract class _SQLTransactionSync native "*SQLTransactionSync" {
 }