code: function _findMatchingGlob(pathData, filename) {
          var globs = Object.keys(pathData),
              globCounter;
  
          if (!filename) {
              return;
          }
  
          for (globCounter = 0; globCounter < globs.length; globCounter++) {
              var glob = globs[globCounter];
  
              if (globmatch(filename, glob)) {
                  return glob;
              }
          }
      }
docs: Utility functions for the PathLayer 
  @private
  
  Look for a matching file glob among the collection of paths.
  
  @param {Object} pathData The keys are globs and the values are the preferences for that glob
  @param {string} filename relative filename to match against the globs
  @return {?string} glob pattern that matched, if any