This changes the exception behavior of getRange. It used to accept
a length of zero, no matter what start value. Now the start value
must be a valid list index.

Review URL: https://codereview.chromium.org//12817003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@20064 260f80e4-7a28-3924-810f-c04153c831b5