Use multiroot in ddk to get absolute URIs relative to the app root location.
Use multiroot in ddk to get absolute URIs relative to the app root location.

Change-Id: Ia9ec2463096d05e456ee41ae8b1b3d2781b17a8e
Reviewed-on: https://dart-review.googlesource.com/25681
Commit-Queue: Sigmund Cherem <beaea8fd7d2a56555046ba4f362c8a93e3938576@google.com>
Reviewed-by: Jake Macdonald <28dccc213a1e50b0de348b9cb82c0229ef6b65f0@google.com>

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