Add EfficientLength marker interface to some iterabels.
Add EfficientLength marker interface to some iterabels.

Use that in List.from and other methods to be more efficient when possible.

R=floitsch@google.com

Review URL: https://codereview.chromium.org//26681002

git-svn-id: a8f079e7cfc3a289d8496d7b88aabbd5c45a3053@28575 260f80e4-7a28-3924-810f-c04153c831b5

dart-lang/intl,astashov/intl,astashov/intl