cros: Fix unit_tests crashes in GetBrand() on official builders

chrome/browser/google/google_brand_chromeos.cc

Index: chrome/browser/google/google_brand_chromeos.cc
diff --git a/chrome/browser/google/google_brand_chromeos.cc b/chrome/browser/google/google_brand_chromeos.cc
index 3ef3374c944d17cc5b3c21e9085c83055846967a..8ccec25a6a292428af1c466227b473f48c4ad1aa 100644
--- a/chrome/browser/google/google_brand_chromeos.cc
+++ b/chrome/browser/google/google_brand_chromeos.cc
@@ -59,7 +59,9 @@ std::string GetBrand() {
          content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
   if (g_brand_empty)
     return std::string();
-  DCHECK(g_browser_process->local_state());
+  // Unit tests do not have prefs.
+  if (!g_browser_process->local_state())
+    return std::string();
   return g_browser_process->local_state()->GetString(prefs::kRLZBrand);
 }