gistfile1.txt

    if (AppConstants.platform == "android") {
      let enginesFromURLs = await this._loadFromChromeURLs(engines, isReload);
      enginesFromURLs.forEach(this._addEngineToStore, this);
    } else {
      for (let [id, locales] of engineLocales) {
        await this._ensureEngine(id, locales);
      }
    }

  async _ensureEngine(id, locales) {
    SearchUtils.log("_ensureEngine " + id);
    try {
      let policy = WebExtensionPolicy.getByID(id);
      if (!policy) {
        SearchUtils.log("_loadEngines: Installing " + id);
        let path = EXT_SEARCH_PREFIX + id.split("@")[0] + "/";
        await AddonManager.installBuiltinAddon(path);
        // The AddonManager will install the engine asynchronously
        // We can manually wait on that happening here.
        await ExtensionParent.apiManager.global.pendingSearchSetupTasks.get(id);
        policy = WebExtensionPolicy.getByID(id)
      }

      await policy.readyPromise;
      await this._installExtensionEngine(policy.extension, locales);
      SearchUtils.log("_ensureEngine: " + id + " installed.");
    } catch (err) {
      Cu.reportError("Failed to install engine: " + err.message + "\n" + err.stack);
    }
  },