[code coverage] Set a default coverage output directory for junit tests

Currently only set default output directory for instrumentation tests https://cs.chromium.org/chromium/src/build/config/android/internal_rules.gni?type=cs&q=%22--coverage-dir%22&sq=package:chromium&g=0&l=763-772
Should do the same for junit tests as well.
Will use this default directory to collect coverage data on bot.


Bug: 970021
Change-Id: I346a8a1493622e61634eebd340b4a8c1c64e93e3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1641379
Reviewed-by: Eric Stevenson <[email protected]>
Commit-Queue: Yun Liu <[email protected]>
Cr-Commit-Position: refs/heads/master@{#665949}
1 file changed