Add junit tests for //base/android

Adds a gyp and gn build target: base_junit_tests
Adds test suite: base_junit_tests

Depends on https://codereview.chromium.org/1048153002/
BUG=448030,472152

Review URL: https://codereview.chromium.org/1051343002

Cr-Commit-Position: refs/heads/master@{#326861}
3 files changed