Generate more valid configurations in media_vpx_video_decoder_fuzzer.

That helps to bypass some DCHECK()'s and to make the Debug build work.
Also that increases execution speed and helps to find new coverage.
Speed increased ~5-10 times. Also I see lot of NEW testcases while
running locally both Debug and Release builds.

R=jrummell@chromium.org
BUG=644672

Review-Url: https://codereview.chromium.org/2324843004
Cr-Commit-Position: refs/heads/master@{#430921}
1 file changed