[EME] Alias CDMInstance enums to the specification-defined enums

[EME] Alias CDMInstance enums to the specification-defined enums
https://bugs.webkit.org/show_bug.cgi?id=167896

Reviewed by Sam Weinig.

Simplify the enums in the CDMInstance class by simply aliasing them
to the EME specification-defined enums. CDMInstance::KeyStatus and
CDMInstance::MessageType were already direct copies of the
MediaKeyStatus and MediaKeyMessageType enums, while the
CDMInstance::LicenseType had the members as MediaKeySessionType,
but with slightly different names.

No changes in behavior.

* Modules/encryptedmedia/CDMInstance.h:
* Modules/encryptedmedia/MediaKeySession.cpp:
(WebCore::MediaKeySession::generateRequest):
(WebCore::MediaKeySession::update):
* testing/MockCDMFactory.cpp:
(WebCore::MockCDMInstance::requestLicense):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@211855 268f45cc-cd09-0410-ab3c-d52691b4dbfc