code: private void processBrowserFieldAdvancedUsage(String dirName, Node entry) {
      for (Node child : entry.children()) {
        Node value = child.getFirstChild();
  
        checkState(child.isStringKey() && (value.isString() || value.isFalse()));
  
        String path = child.getString();
  
        if (path.startsWith(ModuleLoader.DEFAULT_FILENAME_PREFIX)) {
          path = path.substring(ModuleLoader.DEFAULT_FILENAME_PREFIX.length());
        }
  
        String replacement =
            value.isString()
                ? dirName + value.getString()
                : ModuleLoader.JSC_BROWSER_BLACKLISTED_MARKER;
  
        packageJsonMainEntries.put(dirName + path, replacement);
      }
    }
docs: For browser field entries in package.json files that are used in an advanced manner
  (https://github.com/defunctzombie/package-browser-field-spec/#replace-specific-files---advanced),
  track the entries in that object literal as module file replacements.