Add webapk_client_junit_tests to bots.
Add webapk_client_junit_tests to bots.

Please refer to CL (https://codereview.chromium.org/1971773002/) that
adds the webapk_client_junit_tests target.

BUG=609122

Review-Url: https://codereview.chromium.org/1978863002
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#393708}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk