Allow the default browser check to return "unknown" and reflect that in the UI.

chrome/browser/gtk/options/general_page_gtk.cc

Index: chrome/browser/gtk/options/general_page_gtk.cc
===================================================================
--- chrome/browser/gtk/options/general_page_gtk.cc	(revision 25499)
+++ chrome/browser/gtk/options/general_page_gtk.cc	(working copy)
@@ -693,7 +693,7 @@
     ShellIntegration::DefaultBrowserUIState state) {
   const char* color = NULL;
   std::string text;
-  if (state == ShellIntegration::STATE_DEFAULT) {
+  if (state == ShellIntegration::STATE_IS_DEFAULT) {
     color = kDefaultBrowserLabelColor;
     text = l10n_util::GetStringFUTF8(IDS_OPTIONS_DEFAULTBROWSER_DEFAULT,
         l10n_util::GetStringUTF16(IDS_PRODUCT_NAME));
@@ -701,6 +701,10 @@
     color = kNotDefaultBrowserLabelColor;
     text = l10n_util::GetStringFUTF8(IDS_OPTIONS_DEFAULTBROWSER_NOTDEFAULT,
         l10n_util::GetStringUTF16(IDS_PRODUCT_NAME));
+  } else if (state == ShellIntegration::STATE_UNKNOWN) {
+    color = kNotDefaultBrowserLabelColor;
+    text = l10n_util::GetStringFUTF8(IDS_OPTIONS_DEFAULTBROWSER_UNKNOWN,
+        l10n_util::GetStringUTF16(IDS_PRODUCT_NAME));
   }
   if (color) {
     char* markup = g_markup_printf_escaped(kDefaultBrowserLabelMarkup,