Workaround for 8455

Workaround for 8455

BUG=8455
R=ahe@google.com

Committed: https://code.google.com/p/dart/source/detail?r=22375

[vsm, 2013-05-03 04:56:45]

Peter,

I don't think this is quite the right thing if there is more than one dart
script on the page.  But, I don't think dart2js supports more than one script
right now anyway, so I think we should land your workaround for 8455 for now to
unblock folk.

Beyond that, I want to investigate further.  It appears the currentScript
(without this change) is set correctly on FireFox but not on Safari or Chrome. 
Perhaps there is a bug in the latter two.

Vijay

[ahe, 2013-05-03 06:07:11]

LGTM

I think we just need to be patient:
https://bugs.webkit.org/show_bug.cgi?id=104221

Given how new the property is, I think it is going to be a while before we can
expect this in IE.

This is a side-effect of dart.js. I don't think dart.js is a viable solution for
several reasons, and perhaps we should consider if there are alternatives. I
have observed the following problems:

• The file contains superfluous code for js-interop.

• The file delays loading of dart2js code to an extent that the differences can
be observed. This means certain events become meaningless.

• Starting a web app linking directly to dart2js output is significantly faster
than including dart.js. This becomes a problem as you have to import dart.js
just to enable js-interop.

Removing the js-interop code from dart.js would help developers who can serve
different files based on the client's capabilities. In this situation, they can
bypass dart.js completely to get faster startup.

[kevmoo-old, 2013-05-03 15:06:57]

Is dart.js the problem?

I'm hitting this when I have pages with a few javascript files. Some times
dart.js is picked up as the "main" JS file. Sometimes it's the google analytics
JS file, etc.

Any test for a fix should assume there are many JS files loaded in arbitrary
order. Even if the dev is doing all of the right things for their dart code,
there will always be social networking plugins, analytics tools, etc that are
adding arbitrary JS scripts to a page.

[vsm, 2013-05-03 16:44:07]

Committed patchset #1 manually as r22375 (presubmit successful).