Merge "Clarify MediaDrm#getKeyRequest docs: init and mimeType" into oc-dev

     * @param init container-specific data, its meaning is interpreted based on the

     * mime type provided in the mimeType parameter.  It could contain, for example,

     * the content ID, key ID or other data obtained from the content metadata that is

     * required in generating the key request. init may be null when keyType is

     * KEY_TYPE_RELEASE.

     * @param mimeType identifies the mime type of the content

     * required in generating the key request. May be null when keyType is

     * KEY_TYPE_RELEASE or if the request is a renewal, i.e. not the first key

     * request for the session.

     * @param mimeType identifies the mime type of the content. May be null if the

     * keyType is KEY_TYPE_RELEASE or if the request is a renewal, i.e. not the

     * first key request for the session.

     * @param keyType specifes the type of the request. The request may be to acquire

     * keys for streaming or offline content, or to release previously acquired

     * keys, which are identified by a keySetId.