unittest step2: bye bye to multiple entrypoints for unittest

client/tests/client/dom/HTMLAudioElementTest.dart

 #library('HTMLAudioElementTest');
-#import('../../../../lib/unittest/unittest_dom.dart');
+#import('../../../../lib/unittest/unittest.dart');
+#import('../../../../lib/unittest/dom_config.dart');
 #import('dart:dom');
 
 main() {
 
-  forLayoutTests();
+  useDomConfiguration();
 
   test('constructorTest1', () {
       var audio = new HTMLAudioElement();   // would be new Audio() in JS
       Expect.isTrue(audio != null);
       Expect.isTrue(audio is HTMLAudioElement);
     });
 
   test('constructorTest2', () {
       var audio = new HTMLAudioElement('hahaURL');
       Expect.isTrue(audio != null);
       Expect.isTrue(audio is HTMLAudioElement);
       Expect.isTrue(audio.src.indexOf('hahaURL') >= 0);
     });
 }