Mark Trace Processor Row objects as having dynamic attributes
Mark Trace Processor Row objects as having dynamic attributes

This fixes some pytype errors when working with the trace processor API.

See
https://google.github.io/pytype/faq.html#im-dynamically-populating-a-class--module-using-setattr-or-by-modifying-locals--globals-now-pytype-complains-about-missing-attributes-or-module-members-how-do-i-fix-this

Change-Id: I8abec615bb98df4e9a8b1da65d831213080f465b

google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto