Our testing infrastructure uses exceptions to indicate
errors. assertUnreachable therefore throws an exception to indicate
that it was reached. Therefore, it cannot be used to check that an
exception was thrown using the pattern:

try {
  shouldThrow();
  assertUnreachable();
} catch(e) {
}

Such a test will always pass because assertUnreachable will throw an
exception if shouldThrow does not.

R=ricow@chromium.org

Review URL: http://codereview.chromium.org/7053035

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8117 ce2b1a6d-e550-0410-aec6-3dcde31c8c00