Add test files back to BUILD.gn which were accidentally removed previously.

Change-Id: Ic8678f6334ca6de12bfd0a07509500066ff3a25d
Reviewed-on: https://chromium-review.googlesource.com/c/1318749
Reviewed-by: Ryan Hamilton <[email protected]>
Commit-Queue: Ryan Hamilton <[email protected]>
Cr-Commit-Position: refs/heads/master@{#605861}
1 file changed