Add h.264 AVC SPS parsing for resolution (re-land)

Re-land of noharic@'s CL at  https://webrtc-codereview.appspot.com/48129004
which was reverted due to a Mac compile error which most
likely was a Goma flake (it passed on all trybots).

TBR=stefan@webrtc.org, noharic@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/44329005

Cr-Commit-Position: refs/heads/master@{#9079}
8 files changed