function sendReq(config, reqData, reqHeaders) {
      var deferred = $q.defer(),
          promise = deferred.promise,
          cache,
          cachedResp,
          url = buildUrl(config.url, config.params);

      $http.pendingRequests.push(config);
      promise.then(removePendingReq, removePendingReq);


      if (config.cache && config.method == 'GET') {
        cache = isObject(config.cache) ? config.cache : defaultCache;
      }

      if (cache) {
        cachedResp = cache.get(url);
        if (cachedResp) {
          if (cachedResp.then) {
            // cached request has already been sent, but there is no response yet
            cachedResp.then(removePendingReq, removePendingReq);
            return cachedResp;
          } else {
            // serving from cache
            if (isArray(cachedResp)) {
              resolvePromise(cachedResp[1], cachedResp[0], copy(cachedResp[2]));
            } else {
              resolvePromise(cachedResp, 200, {});
            }
          }
        } else {
          // put the promise for the non-transformed response into cache as a placeholder
          cache.put(url, promise);
        }
      }

      // if we won't have the response in cache, send the request to the backend
      if (!cachedResp) {
        $httpBackend(config.method, url, reqData, done, reqHeaders, config.timeout,
            config.withCredentials);
      }

      return promise;


      /**
       * Callback registered to $httpBackend():
       *  - caches the response if desired
       *  - resolves the raw $http promise
       *  - calls $apply
       */
      function done(status, response, headersString) {
        if (cache) {
          if (isSuccess(status)) {
            cache.put(url, [status, response, parseHeaders(headersString)]);
          } else {
            // remove promise from the cache
            cache.remove(url);
          }
        }

        resolvePromise(response, status, headersString);
        $rootScope.$apply();
      }


      /**
       * Resolves the raw $http promise.
       */
      function resolvePromise(response, status, headers) {
        // normalize internal statuses to 0
        status = Math.max(status, 0);

        (isSuccess(status) ? deferred.resolve : deferred.reject)({
          data: response,
          status: status,
          headers: headersGetter(headers),
          config: config
        });
      }


      function removePendingReq() {
        var idx = indexOf($http.pendingRequests, config);
        if (idx !== -1) $http.pendingRequests.splice(idx, 1);
      }
    }
Makes the request

!!! ACCESSES CLOSURE VARS:
$httpBackend, $config, $log, $rootScope, defaultCache, $http.pendingRequests