Add CSSOM support for CSS layers (#31481)

Instead of just crashing.

tests/wpt/meta/css/css-cascade/all-prop-revert-layer.html.ini

@@ -1,2 +1,2 @@
 [all-prop-revert-layer.html]
-  expected: CRASH
+  expected: TIMEOUT

tests/wpt/meta/css/css-cascade/idlharness.html.ini

@@ -1,2 +1,33 @@
 [idlharness.html]
-  expected: CRASH
+  [CSSScopeRule interface: existence and properties of interface object]
+    expected: FAIL
+
+  [CSSScopeRule interface object length]
+    expected: FAIL
+
+  [CSSScopeRule interface object name]
+    expected: FAIL
+
+  [CSSScopeRule interface: existence and properties of interface prototype object]
+    expected: FAIL
+
+  [CSSScopeRule interface: existence and properties of interface prototype object's "constructor" property]
+    expected: FAIL
+
+  [CSSScopeRule interface: existence and properties of interface prototype object's @@unscopables property]
+    expected: FAIL
+
+  [CSSScopeRule interface: attribute start]
+    expected: FAIL
+
+  [CSSScopeRule interface: attribute end]
+    expected: FAIL
+
+  [Stringification of scope]
+    expected: FAIL
+
+  [CSSScopeRule interface: scope must inherit property "start" with the proper type]
+    expected: FAIL
+
+  [CSSScopeRule interface: scope must inherit property "end" with the proper type]
+    expected: FAIL

tests/wpt/meta/css/css-cascade/layer-cssom-order-reverse-at-property.html.ini

@@ -1,2 +1,6 @@
 [layer-cssom-order-reverse-at-property.html]
-  expected: CRASH
+  [Insert layer invalidates @property]
+    expected: FAIL
+
+  [Delete layer invalidates @property]
+    expected: FAIL

tests/wpt/meta/css/css-cascade/layer-cssom-order-reverse.html.ini

@@ -1,2 +1,6 @@
 [layer-cssom-order-reverse.html]
-  expected: CRASH
+  [Insert layer invalidates @font-face]
+    expected: FAIL
+
+  [Delete layer invalidates @font-face]
+    expected: FAIL

tests/wpt/meta/css/css-cascade/layer-rules-cssom.html.ini

@@ -1,27 +0,0 @@
-[layer-rules-cssom.html]
-  [Basic layer block name]
-    expected: FAIL
-
-  [Anonymous layer block name]
-    expected: FAIL
-
-  [Basic layer statement name]
-    expected: FAIL
-
-  [Layer statement with multiple names]
-    expected: FAIL
-
-  [Nested layer block names]
-    expected: FAIL
-
-  [Nested layer statement name lists]
-    expected: FAIL
-
-  [Import into anonymous layer]
-    expected: FAIL
-
-  [Import into named layer]
-    expected: FAIL
-
-  [Import without layer]
-    expected: FAIL

tests/wpt/meta/css/css-cascade/layer-statement-before-import.html.ini

@@ -1,2 +1,3 @@
 [layer-statement-before-import.html]
-  expected: CRASH
+  [insert other rules before the first layer statement without imports]
+    expected: FAIL

tests/wpt/meta/css/css-cascade/parsing/layer.html.ini

@@ -1,2 +0,0 @@
-[layer.html]
-  expected: CRASH