dumpstate: save background traces when a BR is captured.
Adds a call to perfetto --save-for-bugreport to bugreport.
If a background trace labeled with bugreport_score > 0 is
being recorded when dumpstate is invoked, the tracing daemon
will stop the trace and serialize it into a fixed location
(/data/misc/perfetto-traces/bugreport/systrace.pftrace).
If no background tracing is happening, the command is a no-op.
The trace saving happens in two stages:
1. In the very early stage of dumpstate, the trace is
snapshoted (if in progress). This prevents that further
dumpstate activity pushes out interesting contents from
the trace buffer.
2. In the later stages of dumpstate, the trace is attached
to the bugreport.zip file and cleaned up.
Bug: 170334305
Change-Id: I4278459697a5ed20b20ee99032884874a82a66be
4 files changed