Merge "Add samplerate and bitspersample keys"

        { "colorstandard", METADATA_KEY_COLOR_STANDARD },

        { "colortransfer", METADATA_KEY_COLOR_TRANSFER },

        { "colorrange", METADATA_KEY_COLOR_RANGE },

        { "samplerate", METADATA_KEY_SAMPLERATE },

        { "bitspersample", METADATA_KEY_BITS_PER_SAMPLE },

    };

    static const size_t kNumEntries = sizeof(kKeyMap) / sizeof(kKeyMap[0]);