Start really collecting PSS data for process stats.

The activity manager now uses some heuristics to try to
sample PSS data from processes so that it can get enough
data to over reasonable time have something useful, without
doing it too aggressively.

The current policy is:

1. Whenever a significant global change happens (memory state,
   sceen on or off), we collect PSS from all processes; this will
   not happen more than every 10 minutes.
2. When all activities become idle, we will collect PSS from the
   current top process; this will not happen more than every 2
   minutes per process.
3. We will sample the top-most process's PSS every 5 minutes.
4. When an process's oom adj changes and it has been more than
   30 minutes since PSS has been collected from it, we will
   collect a new PSS sample.
5. If a process changes from service A to service B (meaning it
   has been running a service for a long time), we will collect
   a PSS sample from it.
6. If someone explicitly requests PSS data (for running services
   UI or dumpsys), record that.

Also:

- Finish moving the procstats output all to the new format.
- Record information about processes being killed due to excessive
  wake locks or CPU use in procstats.
- Rework how we structure common vs. per-package process stats to
  make it simpler to deal with.
- Optimize the Debug.getPss() implementation (we use it a lot now).
  Should probably optimize it further at some point.

Change-Id: I179f1f7ae5852c7e567de4127d8457b50d27e0f0
7 files changed