Update tests/html to use r'' strings

tests/html/svg_2_test.dart

 #library('SVG2Test');
 #import('../../pkg/unittest/unittest.dart');
 #import('../../pkg/unittest/html_config.dart');
 #import('dart:html');
 
 // Test that SVG elements explicitly implement the IDL interfaces (is-checks
 // only, see SVGTest3 for behavioural tests).
 
 main() {
 
   insertTestDiv() {
     var element = new Element.tag('div');
-    element.innerHTML = @'''
+    element.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>
 ''';
     document.body.nodes.add(element);
     return element;
   }
 
   useHtmlConfiguration();
 
@@ skipping 15 matching lines @@
       Expect.isTrue(r is SVGLocatable);
 
       // Interfaces not implemented.
       Expect.isFalse(r is SVGNumber);
       Expect.isFalse(r is SVGRect);
       Expect.isFalse(r is SVGSVGElement);
 
       div.remove();
     });
 }