AW docs: document how to see log messages in tests

This documents how to see log messages in tests. This includes
robolectric unit tests, which handles logging differently than on-device
tests.

This also notes that robolectric tests do not require a device, since
the top of the doc says ""except where otherwise noted, all tests
require a device or emulator.

Bug: 918221
Test: tools/md_browser/md_browser.py
Test: Upload to gerrit > open file > click "gitiles"
Change-Id: Ib810c2417b7579f46816438e722637af730d0f1f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1955066
Reviewed-by: Robbie McElrath <[email protected]>
Commit-Queue: Nate Fischer <[email protected]>
Cr-Commit-Position: refs/heads/master@{#722354}
1 file changed