Add support for patch_url field in BuildEvent

R=sergeyberezin@chromium.org
BUG=596226, 538195

Review URL: https://codereview.chromium.org/1815413002

Cr-Mirrored-From: https://chromium.googlesource.com/infra/infra
Cr-Mirrored-Commit: 973851683f1f781af753158575efba90da8518c0
2 files changed