Fix interpretation of tests specified on the command line.

The recipe magic expands the test failure trie using '/' as the
separator in contrast to '.', which is the separator in the test case's
id.

BUG=264859
R=robertshield@chromium.org

Review URL: https://codereview.chromium.org/534303002

Cr-Commit-Position: refs/heads/master@{#293163}

chrome/test/mini_installer/test_installer.py

@@ -305,7 +305,7 @@ def main():
     RunCleanCommand(args.force_clean, variable_expander)
     for test in config.tests:
       # If tests were specified via |tests|, their names are formatted like so:
-      test_name = '%s.%s.%s' % (InstallerTest.__module__,
+      test_name = '%s/%s/%s' % (InstallerTest.__module__,
                                 InstallerTest.__name__,
                                 test['name'])
       if not args.test or test_name in args.test: