Remove unused file_thread_ from AudioDebugFileWriter unit tests.

AudioDebugFileWriter's constructor no longer takes a file thread as parameter since [1].
Remove file thread from unit tests.

[1] https://chromium.googlesource.com/chromium/src/+/4d7742ed008b3b749a757d52f75133dfd5d7f44c

Bug: 689520
Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: I0d824f83818893750775ad4e1b80443e2dcd2c2d
Reviewed-on: https://chromium-review.googlesource.com/827129
Commit-Queue: Marina Ciocea <marinaciocea@chromium.org>
Reviewed-by: Max Morin <maxmorin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#524378}
1 file changed