Fix in multi-package-resolver to support files that will be created later (graph

Fix in multi-package-resolver to support files that will be created later (graph
assumes the Source class exists, even when the file has not been created, we
consider that by default the file will be created on the location for the first
of the searchPaths)

R=vsm@google.com

Committed: https://github.com/dart-lang/dev_compiler/commit/07590c234a18091d094d9fb4b7b091257f1f5d73

[Siggi Cherem (dart-lang), 2015-03-11 20:03:29]

Patchset #1 (id:1) has been deleted

[Siggi Cherem (dart-lang), 2015-03-11 20:03:55]

sigmund@google.com changed reviewers:
+ vsm@google.com

[vsm, 2015-03-11 20:07:51]

lgtm

https://codereview.chromium.org/1001563003/diff/20001/lib/src/checker/multi_p...
File lib/src/checker/multi_package_resolver.dart (right):

https://codereview.chromium.org/1001563003/diff/20001/lib/src/checker/multi_p...
lib/src/checker/multi_package_resolver.dart:29: // prefix. The returned source
will have that `source.exists()` is false.
Does this mean that the directory for generated code must be first on the
searchPath?

Perhaps it's better to make it a separate arg then?

[Siggi Cherem (dart-lang), 2015-03-12 18:26:40]

ptal

https://codereview.chromium.org/1001563003/diff/20001/lib/src/checker/multi_p...
File lib/src/checker/multi_package_resolver.dart (right):

https://codereview.chromium.org/1001563003/diff/20001/lib/src/checker/multi_p...
lib/src/checker/multi_package_resolver.dart:29: // prefix. The returned source
will have that `source.exists()` is false.
On 2015/03/11 20:07:50, vsm wrote:
> Does this mean that the directory for generated code must be first on the
> searchPath?
> 
> Perhaps it's better to make it a separate arg then?

After this and our discussion offline, I decided to take a second shot at this.
Instead of picking one default, I'm allowing to keep the source as null in other
parts of the system, and recover from it later.

[vsm, 2015-03-12 18:30:53]

lgtm

[Siggi Cherem (dart-lang), 2015-03-12 19:50:51]

Committed patchset #2 (id:40001) manually as
07590c234a18091d094d9fb4b7b091257f1f5d73 (presubmit successful).