Add the JS helper function to all libraries where we allow the native syntax.

lib/dom/templates/html/frog/html_frog.darttemplate

Index: lib/dom/templates/html/frog/html_frog.darttemplate
diff --git a/lib/dom/templates/html/frog/html_frog.darttemplate b/lib/dom/templates/html/frog/html_frog.darttemplate
index 82ae5a6282daed612e1f3324da22494799b6afc7..b7631bfdfae7834d0ff11e716045d74c0e72dd6a 100644
--- a/lib/dom/templates/html/frog/html_frog.darttemplate
+++ b/lib/dom/templates/html/frog/html_frog.darttemplate
@@ -75,12 +75,9 @@ class _JsSendPortSync implements SendPortSync {
 
   callSync(var message) {
     var serialized = _serialize(message);
-    var result = _call(_id, serialized);
+    var result =
+        JS('var', @'ReceivePortSync.dispatchCall(#, #)', _id, serialized);
     return _deserialize(result);
   }
 
-  static _call(num id, var message) native @"""
-    return ReceivePortSync.dispatchCall(id, message);
-  """;
-
 }