This CL allows the H264 bitstream parser to abort and
report an error on invalid input rather than crashing, and it fixes
several crashes found when fuzzing.
BUG=webrtc:6454
R=magjed@webrtc.org,pbos@webrtc.org
Review-Url: https://codereview.webrtc.org/2471973003
Cr-Commit-Position: refs/heads/master@{#14929}