MediaRecorder: update to spec (3/3)

- removed MediaRecorderErrorEvent, using error Event instead. [1]
- removed default value of mimeType in the ctor options dictionary,
since the options themselves are optional [2]
- minor include + DEPS cleanup

BUG=262211, 571107

[1] https://github.com/w3c/mediacapture-record/issues/31
[2] https://github.com/w3c/mediacapture-record/issues/40

Review URL: https://codereview.chromium.org/1540303003

Cr-Commit-Position: refs/heads/master@{#367310}
9 files changed