Change cs_line_decoration to pass pre-swizzled width / height values.

[gw3583]

This would be a small performance improvement in the line decoration shader.

See

webrender/webrender/src/prim_store.rs

Line 714 in 12b0f3d

LineOrientation::Horizontal => (inline_size, local_rect.size.height),

[jimblandy]

The code linked above is now here:

webrender/webrender/src/scene_building.rs

Line 2758 in 26a837e

LineOrientation::Horizontal => LayoutSize::new(inline_size, block_size),