This directory (platform2/system_api) contains constants and definitions like D-Bus service names that are shared between Chromium and Chromium OS.

This directory is only for things like headers and .proto files. No implementation should be added.

When writting a .proto file make sure to use:

option optimize_for = LITE_RUNTIME;

This will force usage of a lite protobuf instead of a full/heavy weight protobuf. The browser only links against the light version, so you will get cryptic link errors about missing parts of Message if you define a protobuf here and then try to use it in Chrome. Currently CrOS links against the full protobuffer library, but that might change in the future.

When declaring a protobuf, avoid use of required unless it is exactly what you mean. "Required is Forever" and very rarely should actually be used. Consult Protocol Buffer Basics: C++ for a detailed of this issue.