Revert "Add support for V8 and Firefox stack traces in pkg/stack_trace." This reverts commit r24502. Review URL: https://codereview.chromium.org//17998002 git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart/pkg/stack_trace@24506 260f80e4-7a28-3924-810f-c04153c831b5