Contains scripts to benchmark chrome builds.

There are a variety of different benchmarks you could run, but:

• run_action.py allows you to benchmark a particular build action, across a variety of configurations.
• compare_autoninja.py runs the same autoninja command on several output directories, and generates a database containing performance metrics for each invocation
• ftime.py analyses the output of -ftime-trace for a build to examine where our time was spent, on a micro level, but for a whole build. In particular, it currently analyses the amount of time spent #includeing each file.