Support AES-CBC sample encryption in MediaDrm

    enum Mode {

        kMode_Unencrypted = 0,

        kMode_AES_CTR     = 1,

        // Neither key nor iv are being used in this mode.

        // Each subsample is encrypted w/ an iv of all zeroes.

        kMode_AES_WV      = 2,  // FIX constant

        kMode_AES_WV      = 2,

        kMode_AES_CBC     = 3,

    };

    struct SubSample {

        uint32_t mNumBytesOfEncryptedData;

    };

    struct Pattern {

        // Number of blocks to be encrypted in the pattern. If zero, pattern

        // encryption is inoperative.

        uint32_t mEncryptBlocks;

        // Number of blocks to be skipped (left clear) in the pattern. If zero,

        // pattern encryption is inoperative.

        uint32_t mSkipBlocks;

    };

    CryptoPlugin() {}

    virtual ~CryptoPlugin() {}

            const uint8_t key[16],

            const uint8_t iv[16],

            Mode mode,

            const Pattern &pattern,

            const void *srcPtr,

            const SubSample *subSamples, size_t numSubSamples,

            void *dstPtr,