Auto merge of #26758 - jdm:stacking-context-transform-zero, r=mrobinson

Don't create empty stacking contexts in display lists

A recent change to euclid exposed that our display lists can contain Rects that contain NaN values. These NaNs originate from creating stacking contexts with transforms that scale the horizontal or vertical dimensions to 0. WebRender isn't prepared to handle these, so we need to not produce these empty stacking contexts when building the display list.

---
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #26592 and fix #26590
- [x] There are tests for these changes

tests/wpt/mozilla/meta/MANIFEST.json

@@ -6080,6 +6080,19 @@
       {}
      ]
     ],
+    "stacking-context-empty.html": [
+     "952c73f1680805dc3a976446bb509cb924a6a702",
+     [
+      null,
+      [
+       [
+        "/_mozilla/css/stacking-context-empty-ref.html",
+        "=="
+       ]
+      ],
+      {}
+     ]
+    ],
     "stacking_context_overflow_a.html": [
      "dc379afb77977b0e99a0a8ce3321c9afff236a37",
      [
@@ -10311,6 +10324,10 @@
      "0525bab6b11800d29f90efc7efef0f43165fba01",
      []
     ],
+    "stacking-context-empty-ref.html": [
+     "8006e2413694b0776f000d3b8138bed29812b7cd",
+     []
+    ],
     "stacking_context_overflow_ref.html": [
      "49991c449ab4f42afae6f512a7f184e70d77bc34",
      []

tests/wpt/mozilla/tests/css/stacking-context-empty-ref.html

@@ -0,0 +1 @@
+<p><img src="100x100_green.png">

tests/wpt/mozilla/tests/css/stacking-context-empty.html

@@ -0,0 +1,14 @@
+<link rel="match" href="stacking-context-empty-ref.html">
+<style>
+  div {
+        border-radius: 2px;
+        background: #777;
+        border-bottom: 1px solid #f1f1f1;
+  }
+.test {
+        transform: scaleX(0);
+}
+</style>
+<p><img src="100x100_green.png">
+<div class="test">aaa</div>
+<p><img class="test" src="100x100_green.png">