CopyOutputResult must have a working release callback when received over mojo

cc/ipc/copy_output_result.mojom

Index: cc/ipc/copy_output_result.mojom
diff --git a/cc/ipc/copy_output_result.mojom b/cc/ipc/copy_output_result.mojom
index a925e10d6b4986a1512ecd4820c1c98fc6fce7cb..2ff882e2450921ade622c4be513985713932b6ba 100644
--- a/cc/ipc/copy_output_result.mojom
+++ b/cc/ipc/copy_output_result.mojom
@@ -5,6 +5,7 @@
 module cc.mojom;
 
 import "cc/ipc/texture_mailbox.mojom";
+import "cc/ipc/texture_mailbox_releaser.mojom";
 import "skia/public/interfaces/bitmap.mojom";
 import "ui/gfx/geometry/mojo/geometry.mojom";
 
@@ -12,5 +13,6 @@ import "ui/gfx/geometry/mojo/geometry.mojom";
 struct CopyOutputResult {
   gfx.mojom.Size size;

[danakj, 2017/02/14 17:49:10]

This should be optional, it's only used for texture results:
https://cs.chromium.org/chromium/src/cc/output/copy_output_result.h?rcl=c8e27...

[Saman Sami, 2017/02/14 22:17:04]

Acknowledged.

[danakj, 2017/02/14 23:49:34]

Looks like this shouldn't be ? cuz ? refers to a magic null value which Size
doesn't have, not to the field being optional.

   skia.mojom.Bitmap? bitmap;
-  cc.mojom.TextureMailbox texture_mailbox;
+  TextureMailbox? texture_mailbox;
+  TextureMailboxReleaser? releaser;
 };