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

components/gcm_driver/fake_gcm_client.cc

Index: components/gcm_driver/fake_gcm_client.cc
diff --git a/components/gcm_driver/fake_gcm_client.cc b/components/gcm_driver/fake_gcm_client.cc
index eaa66c894d182fea831ea919e8b275cdc9edd992..f3b53361607ee35dfadb723a8fe3d1f83db13b01 100644
--- a/components/gcm_driver/fake_gcm_client.cc
+++ b/components/gcm_driver/fake_gcm_client.cc
@@ -238,15 +238,28 @@ void FakeGCMClient::PerformDelayedStart() {
 }
 
 void FakeGCMClient::ReceiveMessage(const std::string& app_id,
+                                   const std::string& message_id,
                                    const IncomingMessage& message) {
   DCHECK(ui_thread_->RunsTasksOnCurrentThread());
 
+  MessageReceiptCallback receipt_callback =
+      base::Bind(&FakeGCMClient::SendMessageReceipt,
+                 weak_ptr_factory_.GetWeakPtr(), message_id, app_id);
+
   io_thread_->PostTask(
-      FROM_HERE,
-      base::Bind(&FakeGCMClient::MessageReceived,
-                 weak_ptr_factory_.GetWeakPtr(),
-                 app_id,
-                 message));
+      FROM_HERE, base::Bind(&FakeGCMClient::MessageReceived,
+                            weak_ptr_factory_.GetWeakPtr(), app_id, message,
+                            receipt_callback));
+}
+
+void FakeGCMClient::SendMessageReceipt(const std::string& message_id,
+                                       const std::string& app_id,
+                                       GCMMessageStatus status) {
+  DCHECK(io_thread_->RunsTasksOnCurrentThread());
+
+  receipt_message_id_ = message_id;
+  receipt_app_id_ = app_id;
+  receipt_status_ = status;
 }
 
 void FakeGCMClient::DeleteMessages(const std::string& app_id) {
@@ -302,10 +315,12 @@ void FakeGCMClient::SendFinished(const std::string& app_id,
   }
 }
 
-void FakeGCMClient::MessageReceived(const std::string& app_id,
-                                    const IncomingMessage& message) {
+void FakeGCMClient::MessageReceived(
+    const std::string& app_id,
+    const IncomingMessage& message,
+    const MessageReceiptCallback& receipt_callback) {
   if (delegate_)
-    delegate_->OnMessageReceived(app_id, message);
+    delegate_->OnMessageReceived(app_id, message, receipt_callback);
 }
 
 void FakeGCMClient::MessagesDeleted(const std::string& app_id) {