Update tests/html to use r'' strings

tests/html/svg_3_test.dart

 #library('SVG3Test');
 #import('../../pkg/unittest/unittest.dart');
 #import('../../pkg/unittest/html_config.dart');
 #import('dart:html');
 
 // Test that SVG elements have the operations advertised through all the IDL
 // interfaces.  This is a 'duck typing' test, and does not explicitly use 'is'
 // checks on the expected interfaces (that is in SVGTest2).
 
 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 94 matching lines @@
 
   testRect('rect_SVGTests', checkSVGTests);
   testRect('rect_SVGLangSpace', checkSVGLangSpace);
   testRect('rect_SVGExternalResourcesRequired',
            checkSVGExternalResourcesRequired);
   testRect('rect_SVGStylable', checkSVGStylable);
   testRect('rect_SVGLocatable', checkSVGLocatable);
   testRect('rect_SVGTransformable', checkSVGTransformable);
 
 }