Allow ServiceWorkerResourceReader::ReadData() to return empty handle

Before this CL there was a mojo message validation error as a response
of ReadData() is defined as non-nullable data pipe handle but
ServiceWorkerResourceReaderImpl could return an empty handle when
creating a data pipe fails.

Allow a null handle since there isn't nothing for
ServiceWorkerResourceReaderImpl to do anything other than returning an
empty data pipe handle when creating a data pipe fails.

Bug: 1156082
Change-Id: I1761db595bcc30665d0dcdf5c417f8f6dbcc173b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2631817Reviewed-by: Makoto Shimazu <shimazu@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Kinuko Yasuda <kinuko@chromium.org>
Auto-Submit: Kenichi Ishibashi <bashi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#844440}

components/services/storage/public/mojom/service_worker_storage_control.mojom

@@ -81,10 +81,11 @@ interface ServiceWorkerResourceReader {
       (int32 status,
        network.mojom.URLResponseHead? response_head,
        mojo_base.mojom.BigBuffer? metadata);
-  // Reads the content of the resource associated with this reader.
+  // Reads the content of the resource associated with this reader. `pipe`
+  // can be empty when creating a data pipe fails.
   ReadData(int64 size,
            pending_remote<ServiceWorkerDataPipeStateNotifier> notifier) =>
-      (handle<data_pipe_consumer> pipe);
+      (handle<data_pipe_consumer>? pipe);
 };
 
 // An interface that writes a service worker script (resource) to storage.

content/browser/service_worker/service_worker_cache_writer.cc

@@ -739,6 +739,13 @@ class ServiceWorkerCacheWriter::DataPipeReader
   }
 
   void OnReadData(mojo::ScopedDataPipeConsumerHandle data) {
+    // An invalid handle can be returned when creating a data pipe fails on the
+    // other side of the endpoint.
+    if (!data) {
+      owner_->AsyncDoLoop(net::ERR_FAILED);
+      return;
+    }
+
     data_ = std::move(data);
     watcher_.Watch(data_.get(),
                    MOJO_HANDLE_SIGNAL_READABLE | MOJO_HANDLE_SIGNAL_PEER_CLOSED,