unittest step2: bye bye to multiple entrypoints for unittest

client/tests/client/dom/CanvasUsingHtmlTest.dart

 #library('CanvasUsingHtmlTest');
-#import('../../../../lib/unittest/unittest_dom.dart');
+#import('../../../../lib/unittest/unittest.dart');
+#import('../../../../lib/unittest/dom_config.dart');
 #import('dart:html', prefix: 'html');
 #import('dart:dom');
 
 // Version of Canvas test that implicitly uses dart:html library via unittests.
 
 main() {
   HTMLCanvasElement canvas;
   CanvasRenderingContext2D context;
 
   canvas = document.createElement('canvas');
   canvas.setAttribute('width', '100');
   canvas.setAttribute('height', '100');
   document.body.appendChild(canvas);
   context = canvas.getContext('2d');
 
-  forLayoutTests();
+  useDomConfiguration();
   test('FillStyle', () {
     context.fillStyle = "red";
     context.fillRect(10, 10, 20, 20);
 
     // TODO(vsm): Verify the result once we have the ability to read pixels.
   });
   test('SetFillColor', () {
     // With floats.
     context.setFillColor(10, 10, 10, 10);
     context.fillRect(10, 10, 20, 20);
@@ skipping 18 matching lines @@
     ImageData image = context.createImageData(canvas.width,
                                               canvas.height);
     CanvasPixelArray bytes = image.data;
 
     // FIXME: uncomment when numeric index getters are supported.
     //var byte = bytes[0];
 
     Expect.equals(40000, bytes.length);
   });
 }