Use GL to render preview.

To speed up the preview, we direct the decoder output to a
SurfaceTexture, then draw the texture to a surface. The media
rendering parameters (crop, black-border) are implemented
using different vertex coordinates. The color effects are
implemented using fragment shaders. Currently only three color
effects are implemented, but that's all the appplication uses.

Change-Id: If84439fee572ed37ea077749ef9f2bd4f78703e1