Make Comparable generic.
Make Comparable generic.

It's now allowed to write "class X implements Comparable<X>" to make
X comparable only to X's. The argument type of Comparable<T>.compareTo
is now T.

Review URL: https://codereview.chromium.org//12255055

git-svn-id: 29b42837285a5fdcb6c8ad0409bff8538fc60ed2@18655 260f80e4-7a28-3924-810f-c04153c831b5

astashov/logging,dart-lang/logging