code: function processOrCache(sourceText, moduleId, options, opt_url) {
    if (ENABLE_CACHING) {
      var sourceHash = stringHash(sourceText);
      var resultText = loadFromCache(sourceHash);
      if (resultText) {
        return fixupModuleIds(moduleId, resultText);
      }
    }
  
    resultText = global['wtfi']['process'](
        sourceText, options, opt_url);
    if (ENABLE_CACHING) {
      saveToCache(sourceHash, resultText);
    }
    return fixupModuleIds(moduleId, resultText);
  }
docs: Processes source code for instrumentation, with caching if possible.
  @param {string} sourceText Input source text.
  @param {number} moduleId Unique module ID.
  @param {!Object} options Instrumentation options.
  @param {string=} opt_url Source URL.
  @return {string} Transformed source text.