Note this object is shared among all threads created by server.
This facade does not hold onto a Traceutil proxy as the server may be
long-running while individual tests set up and tear down Traceutil.
WARNING: Use of this facade is discouraged as its functionality is only to download traces that
were collected through other means (such as running the trace binary over ssh). Instead, see
TracingFacade, which allows for control of the tracing system as well.
Gets data from the specified path starting from an optional offset.
Loading and returning the entire file is problematic for large trace files,
so will return up to |MAX_CHUNK_SIZE| bytes at once. The bytes of the file are
returned in a field called |data|. If there is more data to read, then a field
|next_offset| will be returned that indicates where it left off.