Update references to Mojo core and bindings

Update references to Mojo core and bindings

Build fix after recent Dart bindings refactoring.  Now that these libraries are
not included in the snapshot, we need to load them from the mojo package.

R=zra@google.com
TBR=zra@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/ea5a2e179d35d66657998989d8390bdabae7fff9

[zra, 2015-03-23 20:22:33]

zra@google.com changed reviewers:
+ zra@google.com

[zra, 2015-03-23 20:22:34]

lgtm

I don't anticipate further changes along these lines, but for reference, how
should I avoid breakage like this in the future?

[abarth-chromium, 2015-03-23 20:22:42]

Committed patchset #2 (id:20001) manually as
ea5a2e179d35d66657998989d8390bdabae7fff9 (presubmit successful).

[abarth-chromium, 2015-03-23 20:25:23]

On 2015/03/23 at 20:22:34, zra wrote:
> I don't anticipate further changes along these lines, but for reference, how
should I avoid breakage like this in the future?

The way I found these was to grep the code-base for the names of the libraries
you renamed.  Essentially,
s/'dart:mojo.core'/'package:mojo/public/dart/core.dart'/