Add a test for non-axis-aligned clipping

wrench/reftests/clip/clip-45-degree-rotation.yaml

@@ -0,0 +1,35 @@
+# Test that transformed content is clipped properly by clips with a different transform.
+---
+root:
+  items:
+    -
+      bounds: [0, 0, 0, 0]
+      "clip-rect": [0, 0, 0, 0]
+      "clip-and-scroll": 0
+      type: "stacking-context"
+      transform: rotate(45) translate(200, 0)
+      items:
+        -
+          bounds: [0, 0, 300, 300]
+          "clip-rect": [0, 0, 300, 300]
+          "clip-and-scroll": 0
+          type: rect
+          color: red
+        -
+          bounds: [0, 0, 300, 300]
+          "clip-rect": [0, 0, 300, 300]
+          "clip-and-scroll": 0
+          type: clip
+          id: 5
+        -
+          bounds: [0, 0, 0, 0]
+          "clip-rect": [0, 0, 0, 0]
+          "clip-and-scroll": 5
+          type: "stacking-context"
+          transform: rotate(-45) translate(-300, 0)
+          items:
+            -
+              bounds: [0, 0, 1598, 1200]
+              "clip-rect": [0, 0, 1598, 1200]
+              type: rect
+              color: green

wrench/reftests/clip/reftest.list

@@ -1,3 +1,3 @@
 == clip-mode.yaml clip-mode.png
 == clip-ellipse.yaml clip-ellipse.png
-
+== clip-45-degree-rotation.yaml clip-45-degree-rotation-ref.png