Add support for GCM subtypes to desktop Instance ID implementation

components/gcm_driver/instance_id/fake_gcm_driver_for_instance_id.cc

Index: components/gcm_driver/instance_id/fake_gcm_driver_for_instance_id.cc
diff --git a/components/gcm_driver/instance_id/fake_gcm_driver_for_instance_id.cc b/components/gcm_driver/instance_id/fake_gcm_driver_for_instance_id.cc
index 0ee7f0b6320f07f2dafc1f3e97a0102ddd48b5cc..2c328ddd8d806d18976eb202cc8f77e4af9a4d3c 100644
--- a/components/gcm_driver/instance_id/fake_gcm_driver_for_instance_id.cc
+++ b/components/gcm_driver/instance_id/fake_gcm_driver_for_instance_id.cc
@@ -57,9 +57,9 @@ void FakeGCMDriverForInstanceID::GetToken(
     const std::string& scope,
     const std::map<std::string, std::string>& options,
     const GetTokenCallback& callback) {
-  std::string token;
   std::string key = app_id + authorized_entity + scope;
   auto iter = tokens_.find(key);
+  std::string token;
   if (iter != tokens_.end()) {
     token = iter->second;
   } else {