SDK / exoplayer

Added a capturer that can capture output from video renderer into bitmaps. This
class uses SurfaceCapturer to setup a surface, then configures this surface as the
output for a video renderer. Once the output is set, it will capture the
output frames from the video renderer and return them as bitmaps.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=201148184