EME: Require codecs parameter for audio/videoCapabilities

Chrome will no longer allow container-only contentType strings in the
audioCapabilities and videoCapabilities passed to requestMediaKeySystemAccess.
There has been a deprecation message for several releases, so enforce this now.

BUG=605661
TEST=modified tests pass

Review-Url: https://codereview.chromium.org/2686133002
Cr-Commit-Position: refs/heads/master@{#449788}
7 files changed