Fix //third_party/cec to not disable -Wunused-function.

components/leveldb_proto/proto_database_impl.h

Index: components/leveldb_proto/proto_database_impl.h
diff --git a/components/leveldb_proto/proto_database_impl.h b/components/leveldb_proto/proto_database_impl.h
index 42c0dff677fcfa9d9c2f3f12ac78f13087f5f294..77f664cddd6419ee1170541e46bd59597a08b1eb 100644
--- a/components/leveldb_proto/proto_database_impl.h
+++ b/components/leveldb_proto/proto_database_impl.h
@@ -181,9 +181,9 @@ void LoadEntriesFromTaskRunner(LevelDB* database,
   }
 }
 
-void LoadKeysFromTaskRunner(LevelDB* database,
-                            std::vector<std::string>* keys,
-                            bool* success) {
+inline void LoadKeysFromTaskRunner(LevelDB* database,
+                                   std::vector<std::string>* keys,
+                                   bool* success) {
   DCHECK(success);
   DCHECK(keys);
   keys->clear();