Add support for int64 and uint64 in values.h's API.

components/user_prefs/pref_registry_syncable.cc

Index: components/user_prefs/pref_registry_syncable.cc
diff --git a/components/user_prefs/pref_registry_syncable.cc b/components/user_prefs/pref_registry_syncable.cc
index b0e40a2842e4786d8065b218c961b92ab9997220..71c0b7039c69c6c2244dd47d138c037d4fca7f7b 100644
--- a/components/user_prefs/pref_registry_syncable.cc
+++ b/components/user_prefs/pref_registry_syncable.cc
@@ -188,9 +188,7 @@ void PrefRegistrySyncable::RegisterInt64Pref(
     int64 default_value,
     PrefSyncStatus sync_status) {
   RegisterSyncablePreference(
-      path,
-      base::Value::CreateStringValue(base::Int64ToString(default_value)),
-      sync_status);
+      path, new base::StringValue(default_value), sync_status);
 }
 
 void PrefRegistrySyncable::RegisterUint64Pref(
@@ -198,9 +196,7 @@ void PrefRegistrySyncable::RegisterUint64Pref(
     uint64 default_value,
     PrefSyncStatus sync_status) {
   RegisterSyncablePreference(
-      path,
-      base::Value::CreateStringValue(base::Uint64ToString(default_value)),
-      sync_status);
+      path, new base::StringValue(default_value), sync_status);
 }
 
 void PrefRegistrySyncable::RegisterSyncablePreference(