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

components/gcm_driver/gcm_account_mapper_unittest.cc

Index: components/gcm_driver/gcm_account_mapper_unittest.cc
diff --git a/components/gcm_driver/gcm_account_mapper_unittest.cc b/components/gcm_driver/gcm_account_mapper_unittest.cc
index e9013e58aa2ff44118b59206b43274b447120935..495a841fe6f2190135426f5522adc5eae74ef201 100644
--- a/components/gcm_driver/gcm_account_mapper_unittest.cc
+++ b/components/gcm_driver/gcm_account_mapper_unittest.cc
@@ -247,7 +247,8 @@ class GCMAccountMapperTest : public testing::Test {
     return account_mapper_->accounts_;
   }
   void MessageReceived(const std::string& app_id,
-                       const IncomingMessage& message);
+                       const IncomingMessage& message,
+                       const MessageReceiptCallback& optional_receipt_callback);
 
   GCMAccountMapper* mapper() { return account_mapper_.get(); }
 
@@ -293,8 +294,10 @@ void GCMAccountMapperTest::Initialize(
                                   base::Unretained(this)));
 }
 
-void GCMAccountMapperTest::MessageReceived(const std::string& app_id,
-                                           const IncomingMessage& message) {
+void GCMAccountMapperTest::MessageReceived(
+    const std::string& app_id,
+    const IncomingMessage& message,
+    const MessageReceiptCallback& optional_receipt_callback) {
   last_received_app_id_ = app_id;
   last_received_message_ = message;
 }