Fix systrace logging, total paused time, and bytes saved message.

Moved the GC top level systrace logging to be inside of Collector::Run.
This prevents cases where we forgot to call it such as background
compaction. Fixed a unit error regarding total pause time. Fixed
negative bytes saved to use the word "expanded".

Bug: 15702709

Change-Id: Ic2991ecad2daa000d0aee9d559b8bc77d8c160aa
4 files changed