static AggregatedHttpFileBuilder builder(HttpData data, long lastModifiedMillis) {
        requireNonNull(data, "data");
        return new AggregatedHttpFileBuilder(data, lastModifiedMillis)
                .autoDetectedContentType(false); // Can't auto-detect because there's no path or URI.
    }
Returns a new {@link AggregatedHttpFileBuilder} that builds an {@link AggregatedHttpFile} from
the specified {@link HttpData} and {@code lastModifiedMillis}.

@param data the content of the file
@param lastModifiedMillis the last modified time represented as the number of milliseconds
                          since the epoch
core/src/main/java/com/linecorp/armeria/server/file/AggregatedHttpFile.java