Asset load failures in Barback should produce AssetNotFoundExceptions.

Asset load failures in Barback should produce AssetNotFoundExceptions.

Previously they were producing MissingInputExceptions, which is the
class used to communicate to listener's on Barback's error stream that
a transformer failed due to a missing input. The Transformer
documentation said that it should get AssetNotFoundExceptions and
those are easier to serialize anyway.

R=rnystrom@google.com
BUG=17225
Committed: https://code.google.com/p/dart/source/detail?r=33673

[Bob Nystrom, 2014-03-13 22:03:53]

lgtm

[Bob Nystrom, 2014-03-13 22:04:09]

On 2014/03/13 22:03:53, Bob Nystrom wrote:
> lgtm

Don't forget to update the pubspec if you haven't already.

[nweiz, 2014-03-13 23:25:41]

On 2014/03/13 22:04:09, Bob Nystrom wrote:
> On 2014/03/13 22:03:53, Bob Nystrom wrote:
> > lgtm
> 
> Don't forget to update the pubspec if you haven't already.

It's been in "-dev" for a while.

[nweiz, 2014-03-13 23:26:22]

Committed patchset #1 manually as r33673 (presubmit successful).