code: function _resolveUrl(base, url) {
      var /** @type {?} */ parts = _split(encodeURI(url));
      var /** @type {?} */ baseParts = _split(base);
      if (__webpack_require__.i(__WEBPACK_IMPORTED_MODULE_1__facade_lang__["c" /* isPresent */])(parts[_ComponentIndex.Scheme])) {
          return _joinAndCanonicalizePath(parts);
      }
      else {
          parts[_ComponentIndex.Scheme] = baseParts[_ComponentIndex.Scheme];
      }
      for (var /** @type {?} */ i = _ComponentIndex.Scheme; i <= _ComponentIndex.Port; i++) {
          if (__webpack_require__.i(__WEBPACK_IMPORTED_MODULE_1__facade_lang__["d" /* isBlank */])(parts[i])) {
              parts[i] = baseParts[i];
          }
      }
      if (parts[_ComponentIndex.Path][0] == '/') {
          return _joinAndCanonicalizePath(parts);
      }
      var /** @type {?} */ path = baseParts[_ComponentIndex.Path];
      if (__webpack_require__.i(__WEBPACK_IMPORTED_MODULE_1__facade_lang__["d" /* isBlank */])(path))
          path = '/';
      var /** @type {?} */ index = path.lastIndexOf('/');
      path = path.substring(0, index + 1) + parts[_ComponentIndex.Path];
      parts[_ComponentIndex.Path] = path;
      return _joinAndCanonicalizePath(parts);
  }
docs: Resolves a URL.
  @param {?} base The URL acting as the base URL.
  @param {?} url
  @return {?}