Merge "Support blink scan"

    @Result

    public int scan(@NonNull FrontendSettings settings, @ScanType int scanType,

            @NonNull @CallbackExecutor Executor executor, @NonNull ScanCallback scanCallback) {

        if (mScanCallback != null || mScanCallbackExecutor != null) {

        /**

         * Scan can be called again for blink scan if scanCallback and executor are same as before.

         */

        if (((mScanCallback != null) && (mScanCallback != scanCallback))

                || ((mScanCallbackExecutor != null) && (mScanCallbackExecutor != executor))) {

            throw new IllegalStateException(

                    "Scan already in progress.  stopScan must be called before a new scan can be "

                            + "started.");

                    "Different Scan session already in progress.  stopScan must be called "

                        + "before a new scan session can be " + "started.");

        }

        mFrontendType = settings.getType();

        if (mFrontendType == FrontendSettings.TYPE_DTMB) {