Add support for GCM subtypes to desktop Instance ID implementation

google_apis/gcm/engine/unregistration_request.h

Index: google_apis/gcm/engine/unregistration_request.h
diff --git a/google_apis/gcm/engine/unregistration_request.h b/google_apis/gcm/engine/unregistration_request.h
index 06e9d506bdb61dceffd71741d42eed8187a3bc92..dc84c5c018580abee4502f7eabb63e71cd94a502 100644
--- a/google_apis/gcm/engine/unregistration_request.h
+++ b/google_apis/gcm/engine/unregistration_request.h
@@ -64,15 +64,22 @@ class GCM_EXPORT UnregistrationRequest : public net::URLFetcherDelegate {
   struct GCM_EXPORT RequestInfo {
     RequestInfo(uint64_t android_id,
                 uint64_t security_token,
-                const std::string& app_id);
+                const std::string& app_id,
+                bool use_subtype,
+                const std::string& category_for_subtypes);
     ~RequestInfo();
 
     // Android ID of the device.
     uint64_t android_id;
     // Security token of the device.
     uint64_t security_token;
+
     // Application ID.
     std::string app_id;
+    // Whether to send |app_id| to GCM as a "subtype" instead of a "category".
+    bool use_subtype;
+    // Category to send if |use_subtype|.
+    std::string category_for_subtypes;
   };
 
   // Encapsulates the custom logic that is needed to build and process the