Added usefull utility methods to Screen and ScreenContext.

chrome/browser/ui/webui/chromeos/login/base_screen_handler_utils.h

Index: chrome/browser/ui/webui/chromeos/login/base_screen_handler_utils.h
diff --git a/chrome/browser/ui/webui/chromeos/login/base_screen_handler_utils.h b/chrome/browser/ui/webui/chromeos/login/base_screen_handler_utils.h
index af6925cbac4b0d7c0525aa3a1f0b0877a682920c..dd89a0911d34f8ea2e184c0d17a2b6362ef7fd4d 100644
--- a/chrome/browser/ui/webui/chromeos/login/base_screen_handler_utils.h
+++ b/chrome/browser/ui/webui/chromeos/login/base_screen_handler_utils.h
@@ -65,8 +65,10 @@ inline bool ParseValue<const base::DictionaryValue*>(
 template<typename T>
 inline bool GetArg(const base::ListValue* args, size_t index, T* out_value) {
   const base::Value* value;
-  if (!args->Get(index, &value))
+  if (!args->Get(index, &value)) {
+    LOG(ERROR) << "Returning false";

[ygorshenin1, 2014/06/11 10:44:00]

nit: debug code?

[dzhioev (left Google), 2014/06/18 14:43:39]

Yes. Removed.

     return false;
+  }
   return ParseValue(value, out_value);
 }