Correct const accessors in base/values.(h|cc)

base/test/values_test_util.cc

Index: base/test/values_test_util.cc
diff --git a/base/test/values_test_util.cc b/base/test/values_test_util.cc
index 91ce347be77e40b767ec68048c0b67c60c0b19fc..a5667f14b81e9700ef6e248fb1a34efb183302fd 100644
--- a/base/test/values_test_util.cc
+++ b/base/test/values_test_util.cc
@@ -21,7 +21,7 @@ void ExpectDictBooleanValue(bool expected_value,
 void ExpectDictDictionaryValue(const DictionaryValue& expected_value,
                                const DictionaryValue& value,
                                const std::string& key) {
-  DictionaryValue* dict_value = NULL;
+  const DictionaryValue* dict_value = NULL;
   EXPECT_TRUE(value.GetDictionary(key, &dict_value)) << key;
   EXPECT_TRUE(Value::Equals(dict_value, &expected_value)) << key;
 }
@@ -37,7 +37,7 @@ void ExpectDictIntegerValue(int expected_value,
 void ExpectDictListValue(const ListValue& expected_value,
                          const DictionaryValue& value,
                          const std::string& key) {
-  ListValue* list_value = NULL;
+  const ListValue* list_value = NULL;
   EXPECT_TRUE(value.GetList(key, &list_value)) << key;
   EXPECT_TRUE(Value::Equals(list_value, &expected_value)) << key;
 }