CopyOutputResult must have a working release callback when received over mojo

cc/ipc/texture_mailbox_releaser.mojom

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+module cc.mojom;
+
+import "gpu/ipc/common/sync_token.mojom";
+
+// This interface behaves similar to ReleaseCallback but works across process
+// boundaries. Once Release is called, it releases the TextureMailbox that it
+// is associated with.
+interface TextureMailboxReleaser {
+  Release(gpu.mojom.SyncToken sync_token, bool is_lost);
+};