Add nanobench tests for BitmapRegionDecoder

SkBitmapRegionDecoderInterface provides an interface
for multiple implementations of Android's
BitmapRegionDecoder.

We already have correctness tests in DM that will enable us
to compare the quality of our various BRD implementations.

We also need these performance tests to compare the speed
of our various implementations.

BUG=skia:4357

Review URL: https://codereview.chromium.org/1344993003
16 files changed