unittest step2: bye bye to multiple entrypoints for unittest

client/tests/client/dom/WrapperTest.dart

 #library('WrapperTest');
-#import('../../../../lib/unittest/unittest_dom.dart');
+#import('../../../../lib/unittest/unittest.dart');
+#import('../../../../lib/unittest/dom_config.dart');
 #import('dart:dom');
 
 main() {
   HTMLCanvasElement canvas;
   CanvasRenderingContext2D context;
 
   canvas = document.createElement('canvas');
   canvas.id = 'canvas';
   canvas.setAttribute('width', '100');
   canvas.setAttribute('height', '100');
   document.body.appendChild(canvas);
   context = canvas.getContext('2d');
 
-  forLayoutTests();
+  useDomConfiguration(isLayoutTest: true);
   test('DomType', () {
     Expect.isTrue(canvas is DOMType);
     Expect.isTrue(context is DOMType);
   });
   test('ObjectLocalStorage', () {
     final element = document.getElementById('canvas');
     element.dartObjectLocalStorage = 42;
 
     Expect.equals(42, canvas.dynamic.dartObjectLocalStorage);
   });
   test('TypeName', () {
     final element = document.getElementById('canvas');
     Expect.stringEquals('HTMLCanvasElement', element.typeName);
     Expect.stringEquals('HTMLCanvasElement', canvas.dynamic.typeName);
     Expect.stringEquals('CanvasRenderingContext2D', context.dynamic.typeName);
   });
 }