code: static SourceFile extractSourceMap(
        SourceFile jsFile, String sourceMapURL, boolean parseInlineSourceMaps) {
      if (parseInlineSourceMaps && sourceMapURL.startsWith(BASE64_URL_PREFIX)) {
        String extractedString = extractBase64String(sourceMapURL);
        if (extractedString != null) {
          return SourceFile.fromCode(jsFile.getName() + ".inline.map", extractedString);
        }
        return null;
      }
      // TODO(tdeegan): Handle absolute urls here.  The compiler needs to come up with a scheme for
      // properly resolving absolute urls from http:// or the root /some/abs/path/... See b/62544959.
      if (isAbsolute(sourceMapURL)) {
        return null;
      }
      // If not absolute, its relative.
      // TODO(tdeegan): Handle urls relative to //# sourceURL. See the sourcemap spec.
      return getRelativePath(jsFile.getName(), sourceMapURL);
    }
docs: For a given //# sourceMappingUrl, this locates the appropriate sourcemap on disk. This is use
  for sourcemap merging (--apply_input_source_maps) and for error resolution.
  
  @param parseInlineSourceMaps Whether to parse Base64 encoded source maps.