constant: Add support for other expressions WebRender uses.

tests/rust/associated_in_body.rs

@@ -21,5 +21,34 @@ bitflags! {
     }
 }
 
+/// An arbitrary identifier for a native (OS compositor) surface
+#[repr(C)]
+#[derive(Debug, Copy, Clone, Hash, Eq, PartialEq)]
+pub struct NativeSurfaceId(pub u64);
+
+impl NativeSurfaceId {
+    /// A special id for the native surface that is used for debug / profiler overlays.
+    pub const DEBUG_OVERLAY: NativeSurfaceId = NativeSurfaceId(u64::MAX);
+}
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone, Hash, Eq, PartialEq)]
+#[cfg_attr(feature = "capture", derive(Serialize))]
+#[cfg_attr(feature = "replay", derive(Deserialize))]
+pub struct NativeTileId {
+    pub surface_id: NativeSurfaceId,
+    pub x: i32,
+    pub y: i32,
+}
+
+impl NativeTileId {
+    /// A special id for the native surface that is used for debug / profiler overlays.
+    pub const DEBUG_OVERLAY: NativeTileId = NativeTileId {
+        surface_id: NativeSurfaceId::DEBUG_OVERLAY,
+        x: 0,
+        y: 0,
+    };
+}
+
 #[no_mangle]
-pub extern "C" fn root(flags: AlignFlags) {}
+pub extern "C" fn root(flags: AlignFlags, tile: NativeTileId) {}