Don't make assumptions about source encoding in analysis server tests (TBR).
Don't make assumptions about source encoding in analysis server tests (TBR).

On Windows, the encoding of an absolute path like "/foo.dart" contains
a drive letter (e.g. "102file:///e:/foo.dart"); on Mac and Linux it
doesn't.  Call ".encoding" from the test so that we don't depend on
the specific file name encoding in use.

As a side benefit, this makes the test independent of bug 18379.

Review URL: https://codereview.chromium.org//247143009

git-svn-id: c93d8a2297af3b929165606efe145742a534bc71@35327 260f80e4-7a28-3924-810f-c04153c831b5

dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk