Fix test failure with --size-limit

The test didn't verify expected error code with invalid sizes. It
assumed VPX_CODEC_OK.

Added new Encoder class which doesn't run decoding at all. It accepts
expected error code to verify with encoder output.

The encoder behavior was changed in 94a65e8.


Change-Id: I6324d8f744e6c4aa82aa66913923dc140b07bfc9
1 file changed