bisect tool: Adding unit tests for pass/transform level bisect

This patch added unit tests for pass and transformation level bisect to
the bisecting tool. Since no compiler is involved in unit test, it used
cmd_script.py to simulate the output of compiler (to stderr).

BUG=chromium:878954
TEST=Passed all unit tests.

Change-Id: I599c079497333ec24f08f37c3315a16f28c0f887
Reviewed-on: https://chromium-review.googlesource.com/1298384
Commit-Ready: Zhizhou Yang <zhizhouy@google.com>
Tested-by: Zhizhou Yang <zhizhouy@google.com>
Reviewed-by: Caroline Tice <cmtice@chromium.org>
5 files changed