Fix for typing issue (#1942)

See change 169573081

javascript/i18n/phonenumbers/phonenumberutil.js

@@ -1366,10 +1366,14 @@ i18n.phonenumbers.PhoneNumberUtil.prototype.
   */
 i18n.phonenumbers.PhoneNumberUtil.prototype.getSupportedCallingCodes =
     function() {
+  var countryCodesAsStrings =
+      Object.keys(i18n.phonenumbers.metadata.countryCodeToRegionCodeMap);
   return goog.array.join(
       this.getSupportedGlobalNetworkCallingCodes(),
-      Object.keys(i18n.phonenumbers.metadata.countryCodeToRegionCodeMap)
-          .map(key => parseInt(key, 10)));
+      goog.array.map(countryCodesAsStrings,
+      function(callingCode) {
+        return parseInt(callingCode, 10);
+      }));
 };