Bug 1571974: Implement Debug for render_target::LineDecorationJob. r=…

…jrmuizel

Differential Revision: https://phabricator.services.mozilla.com/D60924

[ghsync] From https://hg.mozilla.org/mozilla-central/rev/7c493fcca41f1e65083a17a423729eaa06fe5ec3

webrender/src/render_target.rs

@@ -1050,6 +1050,7 @@ pub struct BlitJob {
 
 #[cfg_attr(feature = "capture", derive(Serialize))]
 #[cfg_attr(feature = "replay", derive(Deserialize))]
+#[derive(Debug)]
 pub struct LineDecorationJob {
     pub task_rect: DeviceRect,
     pub local_size: LayoutSize,