Add test for percentage sizes resolving against subpixel lengths (#35809)

Two floats with `width: 50%` each should fit on the same line,
and four floats with `width: 25%` each should fit on the same line.
That's even if the containing block width, expressed in layout units,
cannot be divided by 2 or 4.
This test checks cases that are tricky for browsers where 1 pixel
are either 60, 64 or 100 layout units.
It passes on other browsers but fails on Servo because of #34665.

Signed-off-by: Oriol Brufau <obrufau@igalia.com>

tests/wpt/meta/MANIFEST.json

@@ -247175,6 +247175,35 @@
        {}
       ]
      ],
+     "percentage-width-subpixels.tentative.html": [
+      "2e85baa0f56366e73b34ba8bcb80de2ddf93ee2f",
+      [
+       null,
+       [
+        [
+         "/css/css-sizing/percentage-width-subpixels.tentative-ref.html",
+         "=="
+        ]
+       ],
+       {
+        "fuzzy": [
+         [
+          null,
+          [
+           [
+            0,
+            255
+           ],
+           [
+            0,
+            120
+           ]
+          ]
+         ]
+        ]
+       }
+      ]
+     ],
      "range-percent-intrinsic-size-1.html": [
       "cae1c96eb6d9a54a33ec8a94c749a52ea2a8a086",
       [
@@ -438068,6 +438097,10 @@
       "34e2ed01e5221369db8669548ec732099bef43e8",
       []
      ],
+     "percentage-width-subpixels.tentative-ref.html": [
+      "698e9644ddc62324d248e4de9d39690f52b33a01",
+      []
+     ],
      "range-percent-intrinsic-size-1-ref.html": [
       "3bacd9e4b8f5919d90f0f20578178e7994a92bf6",
       []

tests/wpt/meta/css/css-sizing/percentage-width-subpixels.tentative.html.ini

@@ -0,0 +1,2 @@
+[percentage-width-subpixels.tentative.html]
+  expected: FAIL