Adds the proto definitions required for the Stackdriver Logging API. This compiles, but I'm unsure whether it's actually correct because there seems to be a lot of copy & paste in the build setup.
git-subtree-dir: third_party/cpp/googleapis git-subtree-mainline: 438050b3d9 git-subtree-split: c873fd3aa1
438050b3d9
c873fd3aa1