[autotest] Add a tool to compare performance of multiple suites

The tool gathers the time used by special tasks/test jobs to a tab-sparated output.
Import the output to google spreadsheet can generate a sheet like this:
https://docs.google.com/a/google.com/spreadsheets/d/1iLPSRAgSVz9rGVusTb2yaHJ88iv0QY3hZI_ZI-RdatI/edit#gid=51630294

BUG=None
TEST=./compare_suite.py --jobs 4105

Change-Id: I0ed2dbaecdec9fd5e3857d4267e612127fdfddae
Reviewed-on: https://chromium-review.googlesource.com/205241
Reviewed-by: Dan Shi <dshi@chromium.org>
Tested-by: Dan Shi <dshi@chromium.org>
Commit-Queue: Dan Shi <dshi@chromium.org>
1 file changed