Add ability to test supported content types to MediaDrm

        // given crypto scheme, which is specified by a UUID.

        virtual bool isCryptoSchemeSupported(const uint8_t uuid[16]) = 0;

        // DrmFactory::isContentTypeSupported can be called to determine

        // if the plugin factory is able to construct plugins that support a

        // given media container format specified by mimeType

        virtual bool isContentTypeSupported(const String8 &mimeType) = 0;

        // Construct a DrmPlugin for the crypto scheme specified by UUID.

        virtual status_t createDrmPlugin(

                const uint8_t uuid[16], DrmPlugin **plugin) = 0;