Tweaked profile significant_difference.

- renamed to 'change_thr'
- now it represents how much the top K leading samples need to change
(in percents) in order to trigger compilation.
- extracted ProfileData & file parsing in profiler.h

Bug: 12877748
Change-Id: I10f66120dd5e68b8a690bfa0e9914c07f63c50d5
5 files changed