Update tests/html to use r'' strings

tests/html/svg_1_test.dart

 #library('SVG1Test');
 #import('../../pkg/unittest/unittest.dart');
 #import('../../pkg/unittest/html_config.dart');
 #import('dart:html');
 
 // Test that SVG is present in dart:html API
 
 main() {
   useHtmlConfiguration();
 
   test('simpleRect', () {
       var div = new Element.tag('div');
       document.body.nodes.add(div);
-      div.innerHTML = @'''
+      div.innerHTML = r'''
 <svg id='svg1' width='200' height='100'>
 <rect id='rect1' x='10' y='20' width='130' height='40' rx='5'fill='blue'></rect>
 </svg>
 
 ''';
 
     var e = document.query('#svg1');
     Expect.isTrue(e != null);
 
     SVGRectElement r = document.query('#rect1');
     Expect.equals(10, r.x.baseVal.value);
     Expect.equals(20, r.y.baseVal.value);
     Expect.equals(40, r.height.baseVal.value);
     Expect.equals(130, r.width.baseVal.value);
     Expect.equals(5, r.rx.baseVal.value);
   });
 
   test('trailing newline', () {
     // Ensures that we handle SVG with trailing newlines.
     var logo = new SVGElement.svg("""
       <svg xmlns="http://www.w3.org/2000/svg" version="1.1">
         <path/>
       </svg>
       """);
 
   expect(logo is SVGElement, true);
 
   });
 }