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

components/gcm_driver/gcm_driver_desktop.cc

Index: components/gcm_driver/gcm_driver_desktop.cc
diff --git a/components/gcm_driver/gcm_driver_desktop.cc b/components/gcm_driver/gcm_driver_desktop.cc
index 599957d2a5979fced996c2440031f4cee4344b7c..434c431cd8abf6d829ea2c50dfa1f97e4a073048 100644
--- a/components/gcm_driver/gcm_driver_desktop.cc
+++ b/components/gcm_driver/gcm_driver_desktop.cc
@@ -53,8 +53,10 @@ class GCMDriverDesktop::IOWorker : public GCMClient::Delegate {
   void OnSendFinished(const std::string& app_id,
                       const std::string& message_id,
                       GCMClient::Result result) override;
-  void OnMessageReceived(const std::string& app_id,
-                         const IncomingMessage& message) override;
+  void OnMessageReceived(
+      const std::string& app_id,
+      const IncomingMessage& message,
+      const MessageReceiptCallback& receipt_callback) override;
   void OnMessagesDeleted(const std::string& app_id) override;
   void OnMessageSendError(
       const std::string& app_id,
@@ -111,6 +113,8 @@ class GCMDriverDesktop::IOWorker : public GCMClient::Delegate {
 
   void RecordDecryptionFailure(const std::string& app_id,
                                GCMEncryptionProvider::DecryptionResult result);
+  void SendMessageReceipt(const MessageReceiptCallback& receipt_callback,
+                          GCMMessageStatus status);
 
   // For testing purpose. Can be called from UI thread. Use with care.
   GCMClient* gcm_client_for_testing() const { return gcm_client_.get(); }
@@ -233,15 +237,13 @@ void GCMDriverDesktop::IOWorker::OnSendFinished(const std::string& app_id,
 
 void GCMDriverDesktop::IOWorker::OnMessageReceived(
     const std::string& app_id,
-    const IncomingMessage& message) {
+    const IncomingMessage& message,
+    const MessageReceiptCallback& receipt_callback) {
   DCHECK(io_thread_->RunsTasksOnCurrentThread());
 
-  ui_thread_->PostTask(
-      FROM_HERE,
-      base::Bind(&GCMDriverDesktop::MessageReceived,
-                 service_,
-                 app_id,
-                 message));
+  ui_thread_->PostTask(FROM_HERE,
+                       base::Bind(&GCMDriverDesktop::MessageReceived, service_,
+                                  app_id, message, receipt_callback));
 }
 
 void GCMDriverDesktop::IOWorker::OnMessagesDeleted(const std::string& app_id) {
@@ -510,6 +512,16 @@ void GCMDriverDesktop::IOWorker::RecordDecryptionFailure(
   gcm_client_->RecordDecryptionFailure(app_id, result);
 }
 
+void GCMDriverDesktop::IOWorker::SendMessageReceipt(
+    const MessageReceiptCallback& receipt_callback,
+    GCMMessageStatus status) {
+  DCHECK(io_thread_->RunsTasksOnCurrentThread());
+
+  // The callback was created by the GCMClient on the IO thead so it is safe to
+  // invoke from here.
+  receipt_callback.Run(status);
+}
+
 GCMDriverDesktop::GCMDriverDesktop(
     std::unique_ptr<GCMClientFactory> gcm_client_factory,
     const GCMClient::ChromeBuildInfo& chrome_build_info,
@@ -1215,15 +1227,21 @@ void GCMDriverDesktop::RemoveCachedData() {
   ClearCallbacks();
 }
 
-void GCMDriverDesktop::MessageReceived(const std::string& app_id,
-                                       const IncomingMessage& message) {
+void GCMDriverDesktop::MessageReceived(
+    const std::string& app_id,
+    const IncomingMessage& message,
+    const MessageReceiptCallback& receipt_callback) {

[Peter Beverloo, 2017/02/13 13:47:07]

nit: it'd be a lot clearer if this were called io_receipt_callback to
distinguish from the other receipt_callbacks.

[harkness, 2017/02/14 19:22:29]

I agree, but I also think everything is better with optional, and I didn't want
to mix things here.

   DCHECK(ui_thread_->RunsTasksOnCurrentThread());
 
   // Drop the event if the service has been stopped.
   if (!gcm_started_)
     return;
 
-  DispatchMessage(app_id, message);
+  // Dispatch the message to the GCMDriver, but wrap the IO bound callback in a
+  // new callback which should be called on the UI thread.
+  DispatchMessage(app_id, message,
+                  base::Bind(&GCMDriverDesktop::DoSendMessageReceipt,
+                             weak_ptr_factory_.GetWeakPtr(), receipt_callback));
 }
 
 void GCMDriverDesktop::MessagesDeleted(const std::string& app_id) {
@@ -1342,4 +1360,14 @@ bool GCMDriverDesktop::TokenTupleComparer::operator()(
   return std::get<2>(a) < std::get<2>(b);
 }
 
+void GCMDriverDesktop::DoSendMessageReceipt(
+    const MessageReceiptCallback& receipt_callback,
+    GCMMessageStatus status) {
+  DCHECK(ui_thread_->RunsTasksOnCurrentThread());
+
+  io_thread_->PostTask(
+      FROM_HERE,
+      base::Bind(&GCMDriverDesktop::IOWorker::SendMessageReceipt,
+                 base::Unretained(io_worker_.get()), receipt_callback, status));

[Peter Beverloo, 2017/02/13 13:47:07]

You can skip the indirection and just invoke |receipt_callback| directly:

  io_thread_->PostTask(FROM_HERE, base::Bind(receipt_callback, status));

That way you don't need GCMDriverDesktop::IOWorker::SendMessageReceipt either.

[harkness, 2017/02/14 19:22:29]

Good point, I'd forgotten that it wasn't being called from anywhere else.

+}
 }  // namespace gcm