603d401fc2
`gclient sync` now grabs Robolectric, JUnit, and their transitive runtime dependencies. They're being stored in a new CIPD package, `flutter/android/robolectric_bundle`. `shell/platform/android/BUILD.gn` has a new target for building the tests, `robolectric_tests`. `testing/run_tests.py` has been extended to build and run the new target. Runs the android tests under "build_and_test_android" on CI. This also adds some very simple sample tests to start with and a README to the java tests directory.