Add support for GCM subtypes to desktop Instance ID implementation

components/gcm_driver/instance_id/instance_id_impl.h

Index: components/gcm_driver/instance_id/instance_id_impl.h
diff --git a/components/gcm_driver/instance_id/instance_id_impl.h b/components/gcm_driver/instance_id/instance_id_impl.h
index fb0069d0aa5c1c4a4e0ef94fe958821754222691..26ffb0a2a2a4da9ee4dbb1037e9a249746059909 100644
--- a/components/gcm_driver/instance_id/instance_id_impl.h
+++ b/components/gcm_driver/instance_id/instance_id_impl.h
@@ -27,7 +27,9 @@ namespace instance_id {
 // InstanceID implementation for desktop and iOS.
 class InstanceIDImpl : public InstanceID {
  public:
-  InstanceIDImpl(const std::string& app_id, gcm::GCMDriver* gcm_driver);
+  InstanceIDImpl(const std::string& app_id,
+                 bool use_subtype,
+                 gcm::GCMDriver* gcm_driver);
   ~InstanceIDImpl() override;
 
   // InstanceID:
@@ -69,6 +71,9 @@ class InstanceIDImpl : public InstanceID {
 
   gcm::InstanceIDHandler* Handler();
 
+  // Whether to send |app_id| to GCM as a "subtype" instead of a "category".
+  bool use_subtype_;
+
   gcm::GCMDelayedTaskController delayed_task_controller_;
 
   // The generated Instance ID.