recipe_engine:
  https://crrev.com/222e52d54fd4816863099034b25b6f74e0e1a06a [package.proto] upgrade to proto3. (iannucci@chromium.org)
  https://crrev.com/70340d7caa58896cbcffcccbc5573dd3b488fc5d [doc/recipes.py] proto3 omits empty fields. (iannucci@chromium.org)
  https://crrev.com/286c6f5ec8db26ee88eae1bd30855a9f3d0cf426 [doc/recipes.py] protobuf is a dict of lists. (iannucci@chromium.org)
  https://crrev.com/78c57c5d69a38ef3db86d9763d539383f98714e6 [doc/recipes.py] Make recipes.py 80-cols. (iannucci@chromium.org)

BUG=

Change-Id: I4c5c9e94e9c64d14ccf0048f1aa392148b5f01c8
Reviewed-on: https://chromium-review.googlesource.com/454888
Commit-Queue: Robbie Iannucci <iannucci@chromium.org>
Reviewed-by: Daniel Jacques <dnj@chromium.org>