Bench Class For More Robust Speed Tests

Bench Class For More Robust Speed Tests

To make speed testing more robust, the AbstractBench runs the
desired code multiple times and report the median run time with
mean absolute deviation around the median.

To use the AbstractBench, simply add it as a parent to your test
class, and implement the run() method (with the code you want to
benchmark).

Sample output for VP9QuantizeTest

  [    BENCH ]      Bypass calculations       4x4  165.8 ms ( ±1.0 ms )
  [    BENCH ]        Full calculations       4x4  165.8 ms ( ±0.9 ms )
  [    BENCH ]      Bypass calculations       8x8  129.7 ms ( ±0.9 ms )
  [    BENCH ]        Full calculations       8x8  130.3 ms ( ±1.4 ms )
  [    BENCH ]      Bypass calculations     16x16  110.3 ms ( ±1.4 ms )
  [    BENCH ]        Full calculations     16x16  110.1 ms ( ±0.9 ms )

Change-Id: I1dd649754cb8c4c621eee2728198ea6a555f38b3