Implement MediaSource support for mojo.

- Implements WebMimeRegistryImpl::supportsMediaSourceMIMEType().
- Changes NullEncryptedMediaPlayerSupport to return a callback
  bound to NOTIMPLEMENTED() for the NeedKeyCB.

BUG=423416
TEST=basic mse player plays!

Review URL: https://codereview.chromium.org/653213002

Cr-Commit-Position: refs/heads/master@{#300012}


CrOS-Libchrome-Original-Commit: 328d4822fc471b4fa3c137656758db752bbb749d
1 file changed
tree: cc9ef6fec30f9264aa862c984d76940581255c71
  1. base/
  2. build/
  3. components/
  4. dbus/
  5. device/
  6. ipc/
  7. mojo/
  8. testing/
  9. third_party/
  10. ui/