Provide a mechanism for the GCM driver to send message receipts to GCM.

components/gcm_driver/gcm_driver_android.h

Index: components/gcm_driver/gcm_driver_android.h
diff --git a/components/gcm_driver/gcm_driver_android.h b/components/gcm_driver/gcm_driver_android.h
index ab5c9f3700aa1087c515270b70c4052e6c31856e..ba13f8435b69509f8cc4162abd1e3435a3b75b17 100644
--- a/components/gcm_driver/gcm_driver_android.h
+++ b/components/gcm_driver/gcm_driver_android.h
@@ -97,6 +97,10 @@ class GCMDriverAndroid : public GCMDriver,
       override;
 
  private:
+  void SendMessageReceipt(GCMMessageStatus status);
+  void DoSendMessageReceipt(const MessageReceiptCallback& callback,
+                            GCMMessageSatus status);

[Peter Beverloo, 2017/02/08 17:09:09]

nit: this won't compile (missing `override`). I hope we can merge these two
methods in either case.

[harkness, 2017/02/09 16:27:30]

Weird that this one isn't included in the components_unitttests target.

+
   base::android::ScopedJavaGlobalRef<jobject> java_ref_;
 
   // Callback for GetGCMStatistics.