[activity.py] Identify Gerrit-style bug annotations in commit messages
[activity.py] Identify Gerrit-style bug annotations in commit messages

Extract bug numbers noted "Bug: 99999" in addition to the older
"BUG=99999" style.

Bug: None
Change-Id: If29139ee2bae3c515748395a846e45ce6995d9ec
Reviewed-on: https://chromium-review.googlesource.com/548718
Reviewed-by: Marc-Antoine Ruel <d2bf0fc09b08f7b0888b3ddab32b3e89c7122c8b@chromium.org>
Commit-Queue: Nicolas Dossou-Gbété <ee5c2ba03f479ddc65e5f4c29560392a20210d70@chromium.org>

CoherentLabs/depot_tools,CoherentLabs/depot_tools