Add support for GCM subtypes to desktop Instance ID implementation

components/gcm_driver/gcm_profile_service.h

Index: components/gcm_driver/gcm_profile_service.h
diff --git a/components/gcm_driver/gcm_profile_service.h b/components/gcm_driver/gcm_profile_service.h
index 84bd2742bab5a9a43ff751db9ee53172408fdba2..9094a08d13761ab9961e983a4d1e6a2ef5282f53 100644
--- a/components/gcm_driver/gcm_profile_service.h
+++ b/components/gcm_driver/gcm_profile_service.h
@@ -56,6 +56,7 @@ class GCMProfileService : public KeyedService {
       base::FilePath path,
       net::URLRequestContextGetter* request_context,
       version_info::Channel channel,
+      const std::string& product_category_for_subtypes,

[jianli, 2016/08/08 22:11:51]

The name |product_category_for_subtypes| is not easy to understand if you just
look at this particular line of code. How about naming it as |gcm_category|?

[johnme, 2016/08/10 13:09:55]

See reply above. gcm_category would be confusing, as neither GCM registrations
nor extension IID tokens use this category; it's only for IID tokens which use
subtypes.

       std::unique_ptr<ProfileIdentityProvider> identity_provider,
       std::unique_ptr<GCMClientFactory> gcm_client_factory,
       const scoped_refptr<base::SequencedTaskRunner>& ui_task_runner,