Perfetto Protobuf definitions

There are three groups of protos in the respective perfetto/X directories:

trace/: This directory contains all protos that are output-ed by Perfetto when capturing a trace.

config/: This directory contains the configuration passed as input to various parts of Perfetto, such as:

• (i) the whole trace config that the Consumer sends to the Perfetto trace daemon.
• (ii) the per-data-source config that the trace daemon relays to each Producer.
• (iii) the per-data-source descriptor that each Producer advertises to the trace daemon when registering.

ipc/: This directory contains the definition of the IPC surface between the Perfetto components (Producer, trace daemon and Consumer(s)). This is relevant only in some Perfetto build configuration (i.e. in Android but not in Chrome).