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

cloud_print/service/service_state.cc

Index: cloud_print/service/service_state.cc
diff --git a/cloud_print/service/service_state.cc b/cloud_print/service/service_state.cc
index a07f8f23d908aaec4eea7ac02b66160fd1450ba5..8007db3b87502d19b446194864a6e51f3eec778e 100644
--- a/cloud_print/service/service_state.cc
+++ b/cloud_print/service/service_state.cc
@@ -103,7 +103,7 @@ bool ServiceState::FromString(const std::string& json) {
   if (!data->GetAsDictionary(&services))
     return false;
 
-  base::DictionaryValue* cloud_print = NULL;
+  const base::DictionaryValue* cloud_print = NULL;
   if (!services->GetDictionary(kCloudPrintJsonName, &cloud_print))
     return false;
 
@@ -208,4 +208,3 @@ bool ServiceState::Configure(const std::string& email,
   xmpp_auth_token_ = LoginToGoogle("chromiumsync", email_, password);
   return IsValid();
 }
-