Fix baselineoptimizer issue when deleting a virtual baseline not controlled by scm

BUG=397678
TEST=BaselineOptimizerTest.test_virtual_root_redundant_with_ancestors_skip_scm_commands_with_file_not_in_scm
R=dpranke@chromium.org

Review URL: https://codereview.chromium.org/423553004

git-svn-id: svn://svn.chromium.org/blink/trunk@178961 bbb929c8-8fbe-4397-9dbb-9b2b20218538