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

components/gcm_driver/gcm_driver.cc

Index: components/gcm_driver/gcm_driver.cc
diff --git a/components/gcm_driver/gcm_driver.cc b/components/gcm_driver/gcm_driver.cc
index 21d30549d07030b043adfa405f0ab45eb6b94931..db6ad414a394ba91b5b5f471005e2a4ee0574a11 100644
--- a/components/gcm_driver/gcm_driver.cc
+++ b/components/gcm_driver/gcm_driver.cc
@@ -278,15 +278,19 @@ void GCMDriver::ClearCallbacks() {
   send_callbacks_.clear();
 }
 
-void GCMDriver::DispatchMessage(const std::string& app_id,
-                                const IncomingMessage& message) {
+void GCMDriver::DispatchMessage(
+    const std::string& app_id,
+    const IncomingMessage& message,
+    const MessageReceiptCallback& optional_receipt_callback) {
   encryption_provider_.DecryptMessage(
       app_id, message, base::Bind(&GCMDriver::DispatchMessageInternal,
-                                  weak_ptr_factory_.GetWeakPtr(), app_id));
+                                  weak_ptr_factory_.GetWeakPtr(), app_id,
+                                  optional_receipt_callback));
 }
 
 void GCMDriver::DispatchMessageInternal(
     const std::string& app_id,
+    const MessageReceiptCallback& optional_receipt_callback,
     GCMEncryptionProvider::DecryptionResult result,
     const IncomingMessage& message) {
   UMA_HISTOGRAM_ENUMERATION("GCM.Crypto.DecryptMessageResult", result,
@@ -295,6 +299,8 @@ void GCMDriver::DispatchMessageInternal(
   switch (result) {
     case GCMEncryptionProvider::DECRYPTION_RESULT_UNENCRYPTED:
     case GCMEncryptionProvider::DECRYPTION_RESULT_DECRYPTED:
+      // TODO(beverloo): When the DefaultAppHandler is gone, call
+      // SendMessageReceipt here if there isn't a valid app handler.
       GetAppHandler(app_id)->OnMessage(app_id, message);
       return;
     case GCMEncryptionProvider::DECRYPTION_RESULT_INVALID_ENCRYPTION_HEADER:
@@ -302,6 +308,7 @@ void GCMDriver::DispatchMessageInternal(
     case GCMEncryptionProvider::DECRYPTION_RESULT_NO_KEYS:
     case GCMEncryptionProvider::DECRYPTION_RESULT_INVALID_SHARED_SECRET:
     case GCMEncryptionProvider::DECRYPTION_RESULT_INVALID_PAYLOAD:
+      optional_receipt_callback.Run(GCMMessageStatus::GCM_DECRYPTION_FAILURE);
       RecordDecryptionFailure(app_id, result);
       return;
   }