Add a compare test for color states

This checks that the red values in all 4 default color states
come out identical to a plain old red png.

testsuite/gsk/compare/color-states.node

@@ -0,0 +1,23 @@
+@cicp "mycolors" {
+  primaries: 1;
+  transfer: 13;
+  matrix: 0;
+  range: full;
+}
+
+color {
+  bounds: 0 0 100 100;
+  color: color(srgb 1 0 0);
+}
+color {
+  bounds: 100 0 100 100;
+  color: color(srgb-linear 1 0 0);
+}
+color {
+  bounds: 0 100 100 100;
+  color: color(rec2100-pq 0.792 0.231 0.0738);
+}
+color {
+  bounds: 100 100 100 100;
+  color: color("mycolors" 1 0 0);
+}

testsuite/gsk/meson.build

@@ -46,6 +46,7 @@ compare_render_tests = [
   'color-matrix-identity',
   'color-matrix-merge',
   'color-matrix-parsing',
+  'color-states',
   'conic-gradient-with-64-colorstops',
   'container-single-child-offscreen-for-opacity',
   'crossfade-clip-both-children',