Add execute_after_browser_creation FakeBrowserFinderOptions hook.
Add execute_after_browser_creation FakeBrowserFinderOptions hook.

This is needed to simulate the kinds of failures seen on the waterfall
in Chromium Issue 682819 and get better code coverage for the tests.

BUG=chromium:682819

Review-Url: https://codereview.chromium.org/2644643007

benschmaus/catapult,catapult-project/catapult,sahiljain/catapult,benschmaus/catapult,catapult-project/catapult-csm,sahiljain/catapult,catapult-project/catapult-csm,sahiljain/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult-csm,catapult-project/catapult-csm,benschmaus/catapult,benschmaus/catapult,benschmaus/catapult,sahiljain/catapult,catapult-project/catapult,catapult-project/catapult-csm,benschmaus/catapult,catapult-project/catapult-csm,sahiljain/catapult,catapult-project/catapult-csm,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,sahiljain/catapult,benschmaus/catapult