Fixes to get tavern.dart library working in Spark.

Fixes to get tavern.dart library working in Spark.

Also added a system to the JS logging such that messages will be
buffered during the log window initialization phase.

[pajamallama, 2014-02-06 04:56:09]

I shouldn't be making this many CLs on 2nd last day haha. Probz going to have to
finish them off as a civilian next week.

[tapted, 2014-02-06 05:04:57]

https://codereview.appspot.com/60500043/diff/1/dart/sdk/lib/_internal/pub/lib...
File dart/sdk/lib/_internal/pub/lib/tavern.dart (right):

https://codereview.appspot.com/60500043/diff/1/dart/sdk/lib/_internal/pub/lib...
dart/sdk/lib/_internal/pub/lib/tavern.dart:27: return IO.loadCacheDirectory()
is `IO` defined here yet? I think that needs the new io_wrap that defines it....
Might need to rebase this on an upstream that doesn't have the sandboxed
filesystem for cache

https://codereview.appspot.com/60500043/diff/1/dart/sdk/lib/_internal/pub/lib...
File dart/sdk/lib/_internal/pub/lib/tavern_log.js (right):

https://codereview.appspot.com/60500043/diff/1/dart/sdk/lib/_internal/pub/lib...
dart/sdk/lib/_internal/pub/lib/tavern_log.js:13: document.createTextNode(line) +
'</div>';
ooooh does this work?

You might need 

function appendLogLine(logtext, line, level) {
  div = document.createElement('div');
  div.classList.add('log');
  div.classList.add('log_' + level);
  div.appendChild(document.createTextNode(line));
  logtext.appendChild(div);
}

or similiar

[tapted, 2014-02-06 05:06:58]

https://codereview.appspot.com/60500043/diff/1/dart/sdk/lib/_internal/pub/lib...
File dart/sdk/lib/_internal/pub/lib/tavern_log.js (right):

https://codereview.appspot.com/60500043/diff/1/dart/sdk/lib/_internal/pub/lib...
dart/sdk/lib/_internal/pub/lib/tavern_log.js:13: document.createTextNode(line) +
'</div>';
On 2014/02/06 05:04:58, tapted wrote:
> ooooh does this work?

By this I mean that adding a dom node to a string directly seems crazy ;). I'm
not really sure what that means to do - might be loosely defined.