Add support for GCM subtypes to desktop Instance ID implementation

components/gcm_driver/fake_gcm_client.h

Index: components/gcm_driver/fake_gcm_client.h
diff --git a/components/gcm_driver/fake_gcm_client.h b/components/gcm_driver/fake_gcm_client.h
index 4ba11140e74b9fbcdf3491723be9571ee4cd1859..c9fb383fee5dffc80ffc505755569ed69c7ac72b 100644
--- a/components/gcm_driver/fake_gcm_client.h
+++ b/components/gcm_driver/fake_gcm_client.h
@@ -77,6 +77,7 @@ class FakeGCMClient : public GCMClient {
   void GetInstanceIDData(const std::string& app_id,
                          std::string* instance_id,
                          std::string* extra_data) override;
+  bool CategoryHasSubtype(const std::string& category) override;
   void AddHeartbeatInterval(const std::string& scope, int interval_ms) override;
   void RemoveHeartbeatInterval(const std::string& scope) override;
 
@@ -113,6 +114,7 @@ class FakeGCMClient : public GCMClient {
                            const std::string& message_id);
 
   Delegate* delegate_;
+  std::string category_for_subtypes_;
   bool started_;
   StartMode start_mode_;
   StartModeOverridding start_mode_overridding_;