Make 'where' lazy.

pkg/unittest/lib/html_enhanced_config.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.
 
 /**
  * A simple unit test library for running tests in a browser.
  *
  * Provides enhanced HTML output with collapsible group headers
  * and other at-a-glance information about the test results.
  */
@@ skipping 154 matching lines @@
       for (final test_ in flattened) {
 
         // replace everything but numbers and letters from the group name with
         // '_' so we can use in id and class properties.
         var safeGroup = test_.currentGroup.replaceAll(nonAlphanumeric,'_');
 
         if (test_.currentGroup != previousGroup){
 
           previousGroup = test_.currentGroup;
 
-          var testsInGroup = results.where(
-              (TestCase t) => t.currentGroup == previousGroup);
+          var testsInGroup = results
+              .where((TestCase t) => t.currentGroup == previousGroup)
+              .toList();
           var groupTotalTestCount = testsInGroup.length;
           var groupTestPassedCount = testsInGroup.where(
               (TestCase t) => t.result == 'pass').length;
           groupPassFail = groupTotalTestCount == groupTestPassedCount;
           var passFailClass = "unittest-group-status unittest-group-"
               "status-${groupPassFail ? 'pass' : 'fail'}";
 
           te.elements.add(new Element.html("""
             <div>
               <div id='${safeGroup}'
@@ skipping 218 matching lines @@
   .unittest-row-description
   {
   }
 
   ''';
 }
 
 void useHtmlEnhancedConfiguration([bool isLayoutTest = false]) {
   configure(new HtmlEnhancedConfiguration(isLayoutTest));
 }