Exercise the threaded backend in test bots

We can't draw everything correctly now, but it's at least not crashing.

The draw_to_canvas is modified by adding flush because now the raster
canvas also needs flush like GPU canvases because of the threaded
backend. (Previously, AndroidCodecSrc vetoed GPU (non-raster) sink
and that's why it was not crashing.)


Bug: skia:
Change-Id: I222d706c33e15326e1b97d6bef6c46b8c35cebfd
Reviewed-on: https://skia-review.googlesource.com/118886
Reviewed-by: Kevin Lubick <kjlubick@google.com>
Commit-Queue: Yuqian Li <liyuqian@google.com>
15 files changed