Start transitioning to new API to start Dart.

client/dart.js

Index: client/dart.js
diff --git a/client/dart.js b/client/dart.js
index 7ccf42b9e6609934521c87add98d9654751d9036..d2f17415d2b2e72a337a22c9a00b7f21a71e98c9 100644
--- a/client/dart.js
+++ b/client/dart.js
@@ -4,7 +4,9 @@
 
 // Bootstrap support for Dart scripts on the page as this script.
 
-if (!document.implementation.hasFeature('dart', '1.0')) {
+if (navigator.webkitStartDart) {
+  navigator.webkitStartDart();
+} else if (!document.implementation.hasFeature('dart', '1.0')) {

[vsm, 2012/02/01 15:35:08]

Are you leaving hasFeature for staging purposes only (it's going away right)?
If so, can you add a TODO to remove that check?

Have you tested loading swarm.html or another sample in both dartium and a
non-dart browser?

[antonm, 2012/02/01 17:07:00]

Yes, hasFeature is only left for staging purposes and I've added a TODO as per
your request.

I haven't tested samples.  I'd prefer to submit and check, so I don't have to
patch URLs (which are currently hardcoded to dartlang.org repo).  I was planning
to do it early my local time to be able to revert immediately if anything fails.

But if you prefer that I check it before, I can do that as well.

On 2012/02/01 15:35:08, vsm wrote:

   window.addEventListener("DOMContentLoaded", function (e) {
       // Fall back to compiled JS.
       var scripts = document.getElementsByTagName("script");