Skip the new pub tests on platforms where they don't belong.
Skip the new pub tests on platforms where they don't belong.

Review URL: https://chromiumcodereview.appspot.com//10879071

git-svn-id: a962b240025cf0577aa172e20f49ccb159ba6be1@11338 260f80e4-7a28-3924-810f-c04153c831b5

computmaxer/pub,cjkao/dart-pub,dart-lang/pub,dart-lang/pub,maxwellpeterson-wf/pub