Make line_splitter_test not use multi-line strings.
Make line_splitter_test not use multi-line strings.

Apparently dart2js and the VM disagrees on which characters are in
a multi-line string if the source uses Windows line endings.

Fixes issue 23856

BUG= http://dartbug.com/23856
R=sgjesse@google.com

Review URL: https://codereview.chromium.org//1294353003.

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