Change raw string indicator from @ to r.

lib/html/templates/html/dart2js/html_dart2js.darttemplate

Index: lib/html/templates/html/dart2js/html_dart2js.darttemplate
diff --git a/lib/html/templates/html/dart2js/html_dart2js.darttemplate b/lib/html/templates/html/dart2js/html_dart2js.darttemplate
index 1274c7ecdc404047d278b41862a99779a0bd4474..2a0c6d09755a0b7b0eefce697437b6b63bc6e465 100644
--- a/lib/html/templates/html/dart2js/html_dart2js.darttemplate
+++ b/lib/html/templates/html/dart2js/html_dart2js.darttemplate
@@ -52,7 +52,7 @@ class _HTMLElementImpl extends _ElementImpl native "*HTMLElement" {
 }
 
 // Support for Send/ReceivePortSync.
-int _getNewIsolateId() native @'''
+int _getNewIsolateId() native r'''
   if (!window.$dart$isolate$counter) {
     window.$dart$isolate$counter = 1;
   }
@@ -61,7 +61,7 @@ int _getNewIsolateId() native @'''
 
 // Fast path to invoke JS send port.
 _callPortSync(int id, message) {
-  return JS('var', @'ReceivePortSync.dispatchCall(#, #)', id, message);
+  return JS('var', r'ReceivePortSync.dispatchCall(#, #)', id, message);
 }
 
 // TODO(vsm): Plumb this properly.