layout: Round clientTop, etc queries to pixels properly (#31187)

* layout: Round getClientRect queries to pixels properly

Instead of just flooring all pixels in getClientRect queries, we should
round the rectangle.

* Fix scrollWidth/scrollHeight too, and tests

* Tests passing

* Test expectation for legacy layout

---------

Co-authored-by: Oriol Brufau <obrufau@igalia.com>

tests/wpt/meta/css/cssom-view/subpixel-sizes-and-offsets.tentative.html.ini

@@ -0,0 +1,24 @@
+[subpixel-sizes-and-offsets.tentative.html]
+  [clientWidth, offsetWidth and scrollWidth round 5.5 to 6]
+    expected: FAIL
+
+  [clientWidth, offsetWidth and scrollWidth round 5.9 to 6]
+    expected: FAIL
+
+  [clientHeight, offsetHeight and scrollHeight round 5.1 to 5]
+    expected: FAIL
+
+  [clientHeight, offsetHeight and scrollHeight round 5.5 to 6]
+    expected: FAIL
+
+  [clientHeight, offsetHeight and scrollHeight round 5.9 to 6]
+    expected: FAIL
+
+  [clientLeft and clientTop don't round 44.9]
+    expected: FAIL
+
+  [clientLeft and clientTop don't round 44.5]
+    expected: FAIL
+
+  [clientLeft and clientTop don't round 44.1]
+    expected: FAIL

tests/wpt/meta/css/cssom-view/table-border-collapse-client-width-height.html.ini

@@ -1,3 +0,0 @@
-[table-border-collapse-client-width-height.html]
-  [Table's clientWidth/Height and OffsetWidth/Height should be the same]
-    expected: FAIL

tests/wpt/meta/css/cssom-view/table-border-separate-client-width-height.html.ini

@@ -1,3 +0,0 @@
-[table-border-separate-client-width-height.html]
-  [Table's clientWidth/Height and OffsetWidth/Height should be the same]
-    expected: FAIL