Simplify how PssInstrumentation works.

The Debug.getPss() call is a simpler and more reliable way of getting
the info needed. (This returns a long, and the current implementation
will fail if the PSS exceeds 2 TB, but that's a way off...)

Bug: 119109396
Test: atest libcore-memory-metrics-tests --verbose
Change-Id: I79917c0487b2b2cd3f70716a4baa529d280d8be5
1 file changed