Protect CPU watchdog against short reads.
Protect CPU watchdog against short reads.

We were expecting to read all of /proc/self/stat in one go. We could get
interrupted while reading (I did not find any documentation that states
otherwise).

Bug: 153057698
Change-Id: Iccd94ee5d77448fa4a61e3fb98d56fdedea4a0ea
google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto