Implement new gray mock.

chrome/browser/ui/gtk/gtk_theme_service.cc

Index: chrome/browser/ui/gtk/gtk_theme_service.cc
diff --git a/chrome/browser/ui/gtk/gtk_theme_service.cc b/chrome/browser/ui/gtk/gtk_theme_service.cc
index 0da4875528d026645a9c8693901ac583f41f4fb7..8039a36930b4e7f6f0eb9a6941bbfcf46617fea1 100644
--- a/chrome/browser/ui/gtk/gtk_theme_service.cc
+++ b/chrome/browser/ui/gtk/gtk_theme_service.cc
@@ -603,6 +603,9 @@ GdkPixbuf* GtkThemeService::GetDefaultFavicon(bool native) {
 
 // static
 bool GtkThemeService::DefaultUsesSystemTheme() {
+#if defined(OS_CHROMEOS)
+  return false;
+#else
   scoped_ptr<base::Environment> env(base::Environment::Create());
 
   switch (base::nix::GetDesktopEnvironment(env.get())) {
@@ -612,6 +615,7 @@ bool GtkThemeService::DefaultUsesSystemTheme() {
     default:
       return false;
   }
+#endif
 }
 
 void GtkThemeService::ClearAllThemeData() {