base: Add AsList() function to Value API.

chrome/test/automation/value_conversion_traits.cc

Index: chrome/test/automation/value_conversion_traits.cc
diff --git a/chrome/test/automation/value_conversion_traits.cc b/chrome/test/automation/value_conversion_traits.cc
index f5c1f2c00ac66f7278b5cffa3243705ed2ac72dd..801b80a2d7248c7095e96557491baa9340d15a02 100644
--- a/chrome/test/automation/value_conversion_traits.cc
+++ b/chrome/test/automation/value_conversion_traits.cc
@@ -71,14 +71,15 @@ Value* ValueConversionTraits<ListValue*>::CreateValueFrom(const ListValue* t) {
 
 bool ValueConversionTraits<ListValue*>::SetFromValue(const Value* value,
                                                      ListValue** t) {
-  if (!value->IsType(Value::TYPE_LIST))
+  const ListValue* list = value->AsList();
+  if (!list)
     return false;
-  *t = static_cast<const ListValue*>(value)->DeepCopy();
+  *t = list->DeepCopy();
   return true;
 }
 
 bool ValueConversionTraits<ListValue*>::CanConvert(const Value* value) {
-  return value->IsType(Value::TYPE_LIST);
+  return value->AsList();
 }
 
 Value* ValueConversionTraits<DictionaryValue*>::CreateValueFrom(