Fix FTP directory listing page error by adding "language" key

Also shuffle some test code around so bugs like this can be more easily
noticed by bots.

R=mmenke@chromium.org
BUG=615626

Review-Url: https://codereview.chromium.org/2032903004
Cr-Commit-Position: refs/heads/master@{#398212}

chrome/common/net/net_resource_provider.cc

@@ -37,6 +37,8 @@ struct LazyDirectoryListerCacher {
                     l10n_util::GetStringUTF16(IDS_DIRECTORY_LISTING_SIZE));
     value.SetString("headerDateModified",
         l10n_util::GetStringUTF16(IDS_DIRECTORY_LISTING_DATE_MODIFIED));
+    value.SetString("language",
+                    l10n_util::GetLanguage(base::i18n::GetConfiguredLocale()));
     value.SetString("listingParsingErrorBoxText",
         l10n_util::GetStringFUTF16(IDS_DIRECTORY_LISTING_PARSING_ERROR_BOX_TEXT,
             l10n_util::GetStringUTF16(IDS_PRODUCT_NAME)));