Update htmlescape to new package layout.
Update htmlescape to new package layout.

Review URL: https://codereview.chromium.org//10910239

git-svn-id: a8f079e7cfc3a289d8496d7b88aabbd5c45a3053@12283 260f80e4-7a28-3924-810f-c04153c831b5

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