Refactor Future constructors.

BUG=

Review URL: https://codereview.chromium.org//14070010

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart/pkg/http@21517 260f80e4-7a28-3924-810f-c04153c831b5
3 files changed
tree: b4ff6283b44a20d1ee69cc5c79ac0b4cc0d8de57
  1. lib/
  2. test/
  3. pubspec.yaml