CopyOutputRequest must have a working result_callback_ when received over mojo

cc/ipc/copy_output_request.mojom

Index: cc/ipc/copy_output_request.mojom
diff --git a/cc/ipc/copy_output_request.mojom b/cc/ipc/copy_output_request.mojom
index c6ff8becf5694be7bc0c03d82d9aa1754712c99a..106a95329988617ad3a78af7c3aa9d2a4e54f119 100644
--- a/cc/ipc/copy_output_request.mojom
+++ b/cc/ipc/copy_output_request.mojom
@@ -4,15 +4,22 @@
 
 module cc.mojom;
 
+import "cc/ipc/copy_output_result.mojom";
 import "cc/ipc/texture_mailbox.mojom";
 import "mojo/common/unguessable_token.mojom";
 import "ui/gfx/geometry/mojo/geometry.mojom";
 
 // See cc/output/copy_output_request.h.
-// Note: result_callback_ is not included in this struct.
 struct CopyOutputRequest {
   mojo.common.mojom.UnguessableToken? source;
   bool force_bitmap_result;
   gfx.mojom.Rect? area;
-  cc.mojom.TextureMailbox? texture_mailbox;
+  TextureMailbox? texture_mailbox;
+  CopyOutputResultSender? result_sender;

[danakj, 2017/02/15 19:48:19]

How come this is nullable? (Sorry for being forever confused about this)

+};
+
+// When the display compositor is ready to respond to the CopyOutputRequest,
+// it uses this interface to send back the result.
+interface CopyOutputResultSender {
+  SendResult(CopyOutputResult result);
 };