fix embedder on Windows - fixes #25498

* fixes embedder bugs on Windows
* updates embedder tests to properly test Windows

R=brianwilkerson@google.com

Committed: https://github.com/dart-lang/sdk/commit/d48687078725e477486189befd029057fe750efe

[danrubel, 2016-01-22 19:26:38]

https://codereview.chromium.org/1612393002/diff/1/pkg/analyzer/test/utils.dart
File pkg/analyzer/test/utils.dart (right):

https://codereview.chromium.org/1612393002/diff/1/pkg/analyzer/test/utils.dar...
pkg/analyzer/test/utils.dart:17: JavaFile.pathContext = context ?? path.posix;
Ultimately, we need to remove the line above... but it will take a number of
other CLs before we can do that.

[danrubel, 2016-01-28 03:21:31]

Description was changed from

==========
update embedder test to properly test Windows

This CL is not yet complete, but open for comments on the testing functionality.
This runs properly on Linux/Mac, but I need to run this on Windows and update
the CL with embedder fixes.
==========

to

==========
* fixes embedder bugs on Windows
* updates embedder tests to properly test Windows
==========

[danrubel, 2016-01-28 03:21:47]

danrubel@google.com changed reviewers:
+ brianwilkerson@google.com

[Brian Wilkerson, 2016-01-28 14:20:38]

LGTM

[danrubel, 2016-01-28 15:50:59]

Description was changed from

==========
* fixes embedder bugs on Windows
* updates embedder tests to properly test Windows
==========

to

==========
* fixes embedder bugs on Windows
* updates embedder tests to properly test Windows

R=brianwilkerson@google.com

Committed:
https://github.com/dart-lang/sdk/commit/d48687078725e477486189befd029057fe750efe
==========

[danrubel, 2016-01-28 15:51:01]

Committed patchset #2 (id:20001) manually as
d48687078725e477486189befd029057fe750efe (presubmit successful).