Test Runner: Allow listing tests on Android. Because of quirks with the Chromium-provided Android test runner, we need to use a few tricks to get the test list output. We add placeholder output for a single test to trick the test runner into thinking it ran the tests successfully. We also add an end marker for the tests list so we can parse the list from the more spammy Android stdout log. Will enable a Python wrapper script to list and run performance tests outside of the GTest harness. Bug: angleproject:6090 Change-Id: I810d4722e9a6efa03ef94208e516401890af1c37 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3062240 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Cody Northrop <cnorthrop@google.com> Reviewed-by: Tim Van Patten <timvp@google.com>