Fix various pub issues.

Fix various pub issues.

* Normalize paths before they're passed to dart2js. It handles "." and
  ".." path components poorly.

* Ensure that paths emitted by list-package-dirs are always absolute and
  normalized for backwards-compatibility with the existing protocol.

* Make Package.listFiles work for an in-memory package.

* Fix an error message expectation in packages_file_test.

R=rnystrom@google.com

Committed: https://github.com/dart-lang/pub/commit/072c5d85f4741bd4eede3eb8d309669b887e3c54

[Bob Nystrom, 2015-07-09 22:47:20]

lgtm

https://codereview.chromium.org/1228683003/diff/1/lib/src/dart.dart
File lib/src/dart.dart (right):

https://codereview.chromium.org/1228683003/diff/1/lib/src/dart.dart#newcode74
lib/src/dart.dart:74: // dart2js chokes on relative paths. Including "/./" can
also confuse it, so
File bugs for these?

[nweiz, 2015-07-09 23:42:44]

https://codereview.chromium.org/1228683003/diff/1/lib/src/dart.dart
File lib/src/dart.dart (right):

https://codereview.chromium.org/1228683003/diff/1/lib/src/dart.dart#newcode74
lib/src/dart.dart:74: // dart2js chokes on relative paths. Including "/./" can
also confuse it, so
On 2015/07/09 22:47:19, Bob Nystrom wrote:
> File bugs for these?

They seem to be closely tied to the specific way we invoke it, which is kind of
weird and non-standard anyway. I can't reproduce them just from the command
line, and I don't think it's worth going through the pain of getting a clean
repro otherwise.

[nweiz, 2015-07-09 23:42:50]

Committed patchset #1 (id:1) manually as
072c5d85f4741bd4eede3eb8d309669b887e3c54 (presubmit successful).