Simplify PhysicalFileSystem implementation.

Simplify PhysicalFileSystem implementation.

- Use Uri.base.resolveUri() to do all necessary normalization and
  conversion to absolute paths.

- Store a URI in _PhysicalFileSystemEntity rather than a path.

- Use `new io.File.fromUri(...)` to access the physical files.

- Fix some minor bugs in physical_file_system_test.dart.

R=sigmund@google.com

Committed: https://github.com/dart-lang/sdk/commit/fef4569eb5a80c72b1f7b89dfac96cd78f2b19cf

[Paul Berry, 2017-01-12 23:10:25]

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

[Siggi Cherem (dart-lang), 2017-01-12 23:13:18]

lgtm, nice

[Paul Berry, 2017-01-12 23:48:52]

Description was changed from

==========
Simplify PhysicalFileSystem implementation.

- Use Uri.base.resolveUri() to do all necessary normalization and
  conversion to absolute paths.

- Store a URI in _PhysicalFileSystemEntity rather than a path.

- Use `new io.File.fromUri(...)` to access the physical files.

- Fix some minor bugs in physical_file_system_test.dart.
==========

to

==========
Simplify PhysicalFileSystem implementation.

- Use Uri.base.resolveUri() to do all necessary normalization and
  conversion to absolute paths.

- Store a URI in _PhysicalFileSystemEntity rather than a path.

- Use `new io.File.fromUri(...)` to access the physical files.

- Fix some minor bugs in physical_file_system_test.dart.

R=sigmund@google.com

Committed:
https://github.com/dart-lang/sdk/commit/fef4569eb5a80c72b1f7b89dfac96cd78f2b19cf
==========

[Paul Berry, 2017-01-12 23:48:54]

Committed patchset #1 (id:1) manually as
fef4569eb5a80c72b1f7b89dfac96cd78f2b19cf (presubmit successful).