diff --git a/testing/web-platform/meta/MANIFEST.json b/testing/web-platform/meta/MANIFEST.json
index cffa92dcfdb2..da97276230bf 100644
--- a/testing/web-platform/meta/MANIFEST.json
+++ b/testing/web-platform/meta/MANIFEST.json
@@ -166297,6 +166297,66 @@
      {}
     ]
    ],
+   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-internal-table-001a.html": [
+    [
+     "/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-internal-table-001a.html",
+     [
+      [
+       "/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-internal-table-001-ref.html",
+       "=="
+      ]
+     ],
+     {}
+    ]
+   ],
+   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-internal-table-001b.html": [
+    [
+     "/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-internal-table-001b.html",
+     [
+      [
+       "/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-internal-table-001-ref.html",
+       "=="
+      ]
+     ],
+     {}
+    ]
+   ],
+   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-no-principal-box-001.html": [
+    [
+     "/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-no-principal-box-001.html",
+     [
+      [
+       "/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-no-principal-box-001-ref.html",
+       "=="
+      ]
+     ],
+     {}
+    ]
+   ],
+   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-containing-block-001.html": [
+    [
+     "/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-containing-block-001.html",
+     [
+      [
+       "/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-containing-block-001-ref.html",
+       "=="
+      ]
+     ],
+     {}
+    ]
+   ],
+   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-stacking-and-clipping-001.html": [
+    [
+     "/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-stacking-and-clipping-001.html",
+     [
+      [
+       "/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-stacking-and-clipping-001-ref.html",
+       "=="
+      ]
+     ],
+     {}
+    ]
+   ],
    "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-stacking-context-001a.html": [
     [
      "/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-stacking-context-001a.html",
@@ -173281,6 +173341,18 @@
      {}
     ]
    ],
+   "css/vendor-imports/mozilla/mozilla-central-reftests/shapes1/float-should-push.html": [
+    [
+     "/css/vendor-imports/mozilla/mozilla-central-reftests/shapes1/float-should-push.html",
+     [
+      [
+       "/css/vendor-imports/mozilla/mozilla-central-reftests/shapes1/float-should-push-ref.html",
+       "=="
+      ]
+     ],
+     {}
+    ]
+   ],
    "css/vendor-imports/mozilla/mozilla-central-reftests/shapes1/shape-outside-border-box-001.html": [
     [
      "/css/vendor-imports/mozilla/mozilla-central-reftests/shapes1/shape-outside-border-box-001.html",
@@ -268365,6 +268437,26 @@
      {}
     ]
    ],
+   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-internal-table-001-ref.html": [
+    [
+     {}
+    ]
+   ],
+   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-no-principal-box-001-ref.html": [
+    [
+     {}
+    ]
+   ],
+   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-containing-block-001-ref.html": [
+    [
+     {}
+    ]
+   ],
+   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-stacking-and-clipping-001-ref.html": [
+    [
+     {}
+    ]
+   ],
    "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-stacking-context-001-ref.html": [
     [
      {}
@@ -270390,6 +270482,11 @@
      {}
     ]
    ],
+   "css/vendor-imports/mozilla/mozilla-central-reftests/shapes1/float-should-push-ref.html": [
+    [
+     {}
+    ]
+   ],
    "css/vendor-imports/mozilla/mozilla-central-reftests/shapes1/reftest.list": [
     [
      {}
@@ -556970,79 +557067,115 @@
    "support"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-001-ref.html": [
-   "1e710115a6ddf673f771a4f668c0be2912609442",
+   "0b5688cf2bed82383c358c80272652df9eafac34",
    "support"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-001.html": [
-   "3688553c5cfd25d76feee6021794cc7273fe6cff",
+   "ae677f9c21fb64a02e0a2d9fb5197038800dcf60",
    "reftest"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-002-ref.html": [
-   "185fa9ad94e9045ca490303e7256fd6ffb2cda03",
+   "92c69890e77216eda8056fc107e1a63ccf01e810",
    "support"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-002.html": [
-   "449b89844cf89f6ba2e3d27620255dab114a0755",
+   "0bcaab50f6db9335f1ae5cf02d440d6b6f5d612f",
    "reftest"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-003-ref.html": [
-   "3189218f9d3312f56f4ffaa04be17db936004c57",
+   "e87010a85ae9ffdcb4fbf6793a77222090bfe72d",
    "support"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-003.html": [
-   "354b9a2fdc94912d917d9528a268e46cae3ff83c",
+   "001e102c7ca511c410b1a0392fead919fd4e9a04",
    "reftest"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-004-ref.html": [
-   "ce9682abc33ecf2e394c63ac5e941d4e50c689eb",
+   "aa96e24835b8ea7d20d476252696ad5472e6097c",
    "support"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-004.html": [
-   "14271abdfab8e9495dd4c8e73bc7ea72ec45dfab",
+   "4dc86fc798bd388f58b239e551c5319fecc6a732",
    "reftest"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-005.html": [
-   "5ab4438dae36c8fa2af8ee2bba12bb60be3837ac",
+   "2c395f72eb7ed6498b390d05227d70ff5fbae87e",
    "reftest"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-006-ref.html": [
-   "a54e26fbb340e92d8049ae84191f7a59149e8bc2",
+   "79a496a7814ee9e1f7cb3688d8e182bb58fb687c",
    "support"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-006.html": [
-   "64b9266835318fb192c4d82319f98f64a8a1c03a",
+   "732f4c88901981765fc91918e1755af0a23a4a59",
    "reftest"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-containing-block-absolute-001-ref.html": [
-   "15047fbe1c488711c1d6c309242eb2d5838f8c7e",
+   "36b131c631aef3e8279af91651ac492341e40359",
    "support"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-containing-block-absolute-001.html": [
-   "e4c76a59f93fe875cd85be120d9b492621c6b13b",
+   "31e0e1a2abab1d54d915021ea158bf3da93cb788",
    "reftest"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-containing-block-fixed-001-ref.html": [
-   "15047fbe1c488711c1d6c309242eb2d5838f8c7e",
+   "36b131c631aef3e8279af91651ac492341e40359",
    "support"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-containing-block-fixed-001.html": [
-   "75da07ab71aaa13d847201e545a07c5048aa4d0a",
+   "ab222e28e7f9060860e910384c9e6e95d3f422be",
    "reftest"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-formatting-context-float-001-ref.html": [
-   "62ecb754d87f4923a9a46f64a0d69da1fafff6a6",
+   "e69eda30a4601b11a6f1d0551c29a4632dfa4276",
    "support"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-formatting-context-float-001.html": [
-   "f81a30fc22f9d90a107724378ca6f8e66ac78fd6",
+   "ee93a0a9794588c33606ed23b343bbe1db231e26",
    "reftest"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-formatting-context-margin-001-ref.html": [
-   "0d45e6ef79bbb757a8b47c06408ffc919a81545a",
+   "5f079f29a5998ee2d811ec693e660512894633d6",
    "support"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-formatting-context-margin-001.html": [
-   "360f5b95b4eef2bf80101f172557f2fe65f57ca7",
+   "045d302528444a645e5b6d2fa824ff2a8983b723",
+   "reftest"
+  ],
+  "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-internal-table-001-ref.html": [
+   "ee338f9f2dd0054acae169489ef73c7d5b1b562c",
+   "support"
+  ],
+  "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-internal-table-001a.html": [
+   "028f9b002b099182d98045b83cbd353e16ab0fb0",
+   "reftest"
+  ],
+  "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-internal-table-001b.html": [
+   "127c86614b76a2d851f36bffecbdafa75e7b25f0",
+   "reftest"
+  ],
+  "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-no-principal-box-001-ref.html": [
+   "f1d384a53c3345a7e8c3ea404bd7a83b30723567",
+   "support"
+  ],
+  "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-no-principal-box-001.html": [
+   "7577aef073596faddef3ce2c72b2537410a4be8d",
+   "reftest"
+  ],
+  "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-containing-block-001-ref.html": [
+   "6d7823a0486acad2c53e10419992a1cdb6ede29d",
+   "support"
+  ],
+  "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-containing-block-001.html": [
+   "ce22eaf6214d0f732195704a91c1424b4f4d8331",
+   "reftest"
+  ],
+  "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-stacking-and-clipping-001-ref.html": [
+   "5de4b9db5002c425b7ed7840f8107662bdb73bce",
+   "support"
+  ],
+  "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-stacking-and-clipping-001.html": [
+   "e3691848b9d0dff5ce6a8faf573b5c59fadd5d87",
    "reftest"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-stacking-context-001-ref.html": [
@@ -557058,7 +557191,7 @@
    "reftest"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/contain/reftest.list": [
-   "f13efa449db3e07a7fcec53072121e9d906f8562",
+   "865b3c38162cfb5ef744335416302ca0960f635e",
    "support"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/counter-styles-3/dependent-builtin-ref.html": [
@@ -561193,8 +561326,16 @@
    "e4736754b5c44b272e94a2988dce8feb2e5478f2",
    "support"
   ],
+  "css/vendor-imports/mozilla/mozilla-central-reftests/shapes1/float-should-push-ref.html": [
+   "f99113a1b1e389df8e87f71d6490af0c3d586325",
+   "support"
+  ],
+  "css/vendor-imports/mozilla/mozilla-central-reftests/shapes1/float-should-push.html": [
+   "7cba915a32e329fb93d3d953c54032cd2d9892cf",
+   "reftest"
+  ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/shapes1/reftest.list": [
-   "cb57bc22f6439ecdb953205569754e4cd23dfede",
+   "e8f636071b589eb99a318d29f5ac4317c8c9dc6d",
    "support"
   ],
   "css/vendor-imports/mozilla/mozilla-central-reftests/shapes1/shape-outside-border-box-001-ref.html": [
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-001-ref.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-001-ref.html
index 9cffaf9a3980..629cb939e013 100644
--- a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-001-ref.html
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-001-ref.html
@@ -5,9 +5,6 @@
   <title>CSS Reftest Reference</title>
   <link rel="author" title="Kyle Zentner" href="mailto:zentner.kyle@gmail.com">
   <style>
-  body {
-    margin: 0;
-  }
   #a {
       width: 150px;
       height: 150px;
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-001.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-001.html
index 5b320e8ae410..0f7874b71e0c 100644
--- a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-001.html
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-001.html
@@ -7,9 +7,6 @@
   <link rel="help" href="http://www.w3.org/TR/css-containment-1/#containment-paint">
   <link rel="match" href="contain-paint-clip-001-ref.html">
   <style>
-  body {
-    margin: 0;
-  }
   .root {
     contain: paint;
     width: 100px;
@@ -31,11 +28,6 @@
     top: -25px;
     left: -25px;
   }
-  .c {
-    width: 100px;
-    height: 100px;
-    background: red;
-  }
   .background {
     position: absolute;
     top: 0;
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-002-ref.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-002-ref.html
index 7b0ca5ec5550..3baefff57cf1 100644
--- a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-002-ref.html
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-002-ref.html
@@ -6,9 +6,6 @@
   <link rel="author" title="Yusuf Sermet" href="mailto:ysermet@mozilla.com">
   <link rel="author" title="Kyle Zentner" href="mailto:zentner.kyle@gmail.com">
   <style>
-  body {
-    margin: 0;
-  }
   .root {
     overflow: hidden;
     width: 100px;
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-002.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-002.html
index eb7c8b32678e..b6fbc9c2927a 100644
--- a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-002.html
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-002.html
@@ -8,9 +8,6 @@
   <link rel="help" href="http://www.w3.org/TR/css-containment-1/#containment-paint">
   <link rel="match" href="contain-paint-clip-002-ref.html">
   <style>
-  body {
-    margin: 0;
-  }
   .root {
     contain: paint;
     width: 100px;
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-003-ref.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-003-ref.html
index 34e79489af79..425844ae4761 100644
--- a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-003-ref.html
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-003-ref.html
@@ -5,9 +5,6 @@
   <title>CSS Reftest Reference</title>
   <link rel="author" title="Kyle Zentner" href="mailto:zentner.kyle@gmail.com">
   <style>
-  body {
-    margin: 0;
-  }
   .root {
     overflow-x: scroll;
     overflow-y: scroll;
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-003.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-003.html
index e02dae14f022..ed270e9e0cca 100644
--- a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-003.html
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-003.html
@@ -7,9 +7,6 @@
   <link rel="help" href="http://www.w3.org/TR/css-containment-1/#containment-paint">
   <link rel="match" href="contain-paint-clip-003-ref.html">
   <style>
-  body {
-    margin: 0;
-  }
   .root {
     contain: paint;
     overflow-y: scroll;
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-004-ref.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-004-ref.html
index 4eda898abedf..0861c68cbe32 100644
--- a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-004-ref.html
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-004-ref.html
@@ -5,9 +5,6 @@
   <title>CSS Reftest Reference</title>
   <link rel="author" title="Kyle Zentner" href="mailto:zentner.kyle@gmail.com">
   <style>
-  body {
-    margin: 0;
-  }
   .root {
     overflow-y: scroll;
     overflow-x: scroll;
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-004.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-004.html
index e3ed254761c7..844a59ad6913 100644
--- a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-004.html
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-004.html
@@ -7,9 +7,6 @@
   <link rel="help" href="http://www.w3.org/TR/css-containment-1/#containment-paint">
   <link rel="match" href="contain-paint-clip-004-ref.html">
   <style>
-  body {
-    margin: 0;
-  }
   .root {
     contain: paint;
     overflow-x: scroll;
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-005.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-005.html
index dc92202640f0..b2766e374e44 100644
--- a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-005.html
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-005.html
@@ -8,11 +8,9 @@
   <link rel="help" href="http://www.w3.org/TR/css-containment-1/#containment-paint">
   <link rel="match" href="contain-paint-clip-003-ref.html">
   <style>
-  body {
-    margin: 0;
-  }
   ul {
     padding: 0;
+    margin: 0;
   }
   .root {
     contain: paint;
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-006-ref.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-006-ref.html
index f3823949600f..ecd22b307a9b 100644
--- a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-006-ref.html
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-006-ref.html
@@ -6,9 +6,6 @@
   <link rel="author" title="Yusuf Sermet" href="mailto:ysermet@mozilla.com">
   <link rel="author" title="Kyle Zentner" href="mailto:zentner.kyle@gmail.com">
   <style>
-  body {
-    margin: 0;
-  }
   .root {
     width: 100px;
     height: 100px;
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-006.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-006.html
index f6ffdc3928e0..14d23f431348 100644
--- a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-006.html
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-006.html
@@ -8,9 +8,6 @@
   <link rel="help" href="http://www.w3.org/TR/css-containment-1/#containment-paint">
   <link rel="match" href="contain-paint-clip-006-ref.html">
   <style>
-  body {
-    margin: 0;
-  }
   .root {
     contain: paint;
     width: 100px;
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-containing-block-absolute-001-ref.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-containing-block-absolute-001-ref.html
index 422706802a2a..8861d19f888a 100644
--- a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-containing-block-absolute-001-ref.html
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-containing-block-absolute-001-ref.html
@@ -5,9 +5,6 @@
   <title>CSS Reftest Reference</title>
   <link rel="author" title="Kyle Zentner" href="mailto:zentner.kyle@gmail.com">
   <style>
-  body {
-    margin: 0;
-  }
   #a {
       width: 100px;
       height: 100px;
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-containing-block-absolute-001.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-containing-block-absolute-001.html
index fc04df008a2f..ef564069eb1f 100644
--- a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-containing-block-absolute-001.html
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-containing-block-absolute-001.html
@@ -7,9 +7,6 @@
   <link rel="help" href="http://www.w3.org/TR/css-containment-1/#containment-paint">
   <link rel="match" href="contain-paint-containing-block-absolute-001-ref.html">
   <style>
-  body {
-    margin: 0;
-  }
   #a {
       contain: paint;
       width: 100px;
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-containing-block-fixed-001-ref.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-containing-block-fixed-001-ref.html
index 422706802a2a..8861d19f888a 100644
--- a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-containing-block-fixed-001-ref.html
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-containing-block-fixed-001-ref.html
@@ -5,9 +5,6 @@
   <title>CSS Reftest Reference</title>
   <link rel="author" title="Kyle Zentner" href="mailto:zentner.kyle@gmail.com">
   <style>
-  body {
-    margin: 0;
-  }
   #a {
       width: 100px;
       height: 100px;
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-containing-block-fixed-001.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-containing-block-fixed-001.html
index 60f180beaab9..fc5ede156e9e 100644
--- a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-containing-block-fixed-001.html
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-containing-block-fixed-001.html
@@ -7,9 +7,6 @@
   <link rel="help" href="http://www.w3.org/TR/css-containment-1/#containment-paint">
   <link rel="match" href="contain-paint-containing-block-fixed-001-ref.html">
   <style>
-  body {
-    margin: 0;
-  }
   #a {
       contain: paint;
       width: 100px;
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-formatting-context-float-001-ref.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-formatting-context-float-001-ref.html
index 5a70a21c1769..ceff7f4569e1 100644
--- a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-formatting-context-float-001-ref.html
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-formatting-context-float-001-ref.html
@@ -5,9 +5,6 @@
   <title>CSS Reftest Reference</title>
   <link rel="author" title="Kyle Zentner" href="mailto:zentner.kyle@gmail.com">
   <style>
-  body {
-    margin: 0;
-  }
   #left {
     float: left;
     height: 50px;
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-formatting-context-float-001.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-formatting-context-float-001.html
index 06a59f2e58d5..e5827209d719 100644
--- a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-formatting-context-float-001.html
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-formatting-context-float-001.html
@@ -7,9 +7,6 @@
   <link rel="help" href="http://www.w3.org/TR/css-containment-1/#containment-paint">
   <link rel="match" href="contain-paint-formatting-context-float-001-ref.html">
   <style>
-  body {
-    margin: 0;
-  }
   #left {
     float: left;
     height: 50px;
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-formatting-context-margin-001-ref.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-formatting-context-margin-001-ref.html
index 6dde7bc90e1e..1976f71bf552 100644
--- a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-formatting-context-margin-001-ref.html
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-formatting-context-margin-001-ref.html
@@ -5,9 +5,6 @@
   <title>CSS Reftest Test</title>
   <link rel="author" title="Kyle Zentner" href="mailto:zentner.kyle@gmail.com">
   <style>
-  body {
-    margin: 0;
-  }
   #a {
       background: blue;
       margin: 10px;
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-formatting-context-margin-001.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-formatting-context-margin-001.html
index fdc0bb7f15e5..d37464228658 100644
--- a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-formatting-context-margin-001.html
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-formatting-context-margin-001.html
@@ -7,9 +7,6 @@
   <link rel="help" href="http://www.w3.org/TR/css-containment-1/#containment-paint">
   <link rel="match" href="contain-paint-formatting-context-margin-001-ref.html">
   <style>
-  body {
-    margin: 0;
-  }
   #a {
       contain: paint;
       background: blue;
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-internal-table-001-ref.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-internal-table-001-ref.html
new file mode 100644
index 000000000000..d23678941e2f
--- /dev/null
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-internal-table-001-ref.html
@@ -0,0 +1,30 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset=utf-8>
+    <title>CSS Reftest Reference</title>
+    <link rel="author" title="Yusuf Sermet" href="mailto:ysermet@mozilla.com">
+    <style>
+      tr {
+        z-index: 10;
+      }
+      th {
+        background-color: blue;
+        padding-left: 50px;
+      }
+      caption {
+        position: fixed;
+        background-color: yellow;
+        z-index: 2;
+      }
+    </style>
+  </head>
+  <body>
+    <table>
+      <caption>PASS</caption>
+      <tr>
+        <th>&emsp;</th>
+      </tr>
+    </table>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-internal-table-001a.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-internal-table-001a.html
new file mode 100644
index 000000000000..283b8b941a4c
--- /dev/null
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-internal-table-001a.html
@@ -0,0 +1,34 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset=utf-8>
+    <title>CSS-contain test: paint containment on internal table elements except table-cell.</title>
+    <link rel="author" title="Yusuf Sermet" href="mailto:ysermet@mozilla.com">
+    <link rel="help" href="http://www.w3.org/TR/css-containment-1/#containment-paint">
+    <link rel="match" href="contain-paint-ignored-cases-internal-table-001-ref.html">
+    <meta name="assert" content="Paint containment should not apply to internal table elements except table-cell. This test testes only the tr element, and confirms contain:paint does not create a stacking context.">
+    <style>
+      tr {
+        contain: paint;
+        z-index: 10;
+      }
+      th {
+        background-color: blue;
+        padding-left: 50px;
+      }
+      caption {
+        position: fixed;
+        background-color: yellow;
+        z-index: 2;
+      }
+    </style>
+  </head>
+  <body>
+    <table>
+      <caption>PASS</caption>
+      <tr>
+        <th>&emsp;</th>
+      </tr>
+    </table>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-internal-table-001b.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-internal-table-001b.html
new file mode 100644
index 000000000000..cff28b8b5c28
--- /dev/null
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-internal-table-001b.html
@@ -0,0 +1,36 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset=utf-8>
+    <title>CSS-contain test: paint containment on internal table elements except table-cell.</title>
+    <link rel="author" title="Yusuf Sermet" href="mailto:ysermet@mozilla.com">
+    <link rel="help" href="http://www.w3.org/TR/css-containment-1/#containment-paint">
+    <link rel="match" href="contain-paint-ignored-cases-internal-table-001-ref.html">
+    <meta name="assert" content="Paint containment should not apply to internal table elements except table-cell. This test testes only the tbody element, and confirms contain:paint does not create a stacking context.">
+    <style>
+      tbody {
+        contain: paint;
+        z-index: 10;
+      }
+      th {
+        background-color: blue;
+        padding-left: 50px;
+      }
+      caption {
+        position: fixed;
+        background-color: yellow;
+        z-index: 2;
+      }
+    </style>
+  </head>
+  <body>
+    <table>
+      <caption>PASS</caption>
+      <tbody>
+        <tr>
+          <th>&emsp;</th>
+        </tr>
+      </tbody>
+    </table>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-no-principal-box-001-ref.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-no-principal-box-001-ref.html
new file mode 100644
index 000000000000..b4513709e513
--- /dev/null
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-no-principal-box-001-ref.html
@@ -0,0 +1,57 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>CSS Reftest Reference</title>
+  <link rel="author" title="Yusuf Sermet" href="mailto:ysermet@mozilla.com">
+  <style>
+    div {
+      position: relative;
+      width: 100px;
+    }
+    #div1,
+    #div3 {
+      background-color: #cfc;
+      height: 100px;
+    }
+    #div1 {
+      z-index: 5;
+    }
+    #div2 {
+      display: contents;
+      background-color: #fdd;
+      height: 100px;
+      top: -20px;
+    }
+    #div2_1 {
+      background-color: #ffc;
+      z-index: 6;
+      top: -10px;
+      height: 100px;
+    }
+    #div2_2 {
+      z-index: 3;
+      position: absolute;
+      top: -15px;
+      width: 40px;
+      height: 300px;
+      background-color: #ddf;
+    }
+    #div3 {
+      z-index: 2;
+      top: -50px;
+    }
+  </style>
+</head>
+<body>
+  <div id="div1"></div>
+
+  <div id="div2">
+    <div id="div2_1"></div>
+
+    <div id="div2_2"></div>
+  </div>
+
+  <div id="div3"></div>
+</body>
+</html>
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-no-principal-box-001.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-no-principal-box-001.html
new file mode 100644
index 000000000000..4b9c90720991
--- /dev/null
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-no-principal-box-001.html
@@ -0,0 +1,61 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>CSS Test: 'contain: paint' with 'display: contents'.</title>
+  <link rel="author" title="Yusuf Sermet" href="mailto:ysermet@mozilla.com">
+  <link rel="help" href="https://drafts.csswg.org/css-contain/#containment-paint">
+  <link rel="match" href="contain-paint-ignored-cases-no-principal-box-001-ref.html">
+  <meta name="assert" content="Contain:paint should have no effect when no principle box is generated.">
+  <style>
+    div {
+      position: relative;
+      width: 100px;
+    }
+    #div1,
+    #div3 {
+      background-color: #cfc;
+      height: 100px;
+    }
+    #div1 {
+      z-index: 5;
+    }
+    #div2 {
+      display: contents;
+      contain: paint;
+      background-color: #fdd;
+      height: 100px;
+      top: -20px;
+    }
+    #div2_1 {
+      background-color: #ffc;
+      z-index: 6;
+      top: -10px;
+      height: 100px;
+    }
+    #div2_2 {
+      z-index: 3;
+      position: absolute;
+      top: -15px;
+      width: 40px;
+      height: 300px;
+      background-color: #ddf;
+    }
+    #div3 {
+      z-index: 2;
+      top: -50px;
+    }
+  </style>
+</head>
+<body>
+  <div id="div1"></div>
+
+  <div id="div2">
+    <div id="div2_1"></div>
+
+    <div id="div2_2"></div>
+  </div>
+
+  <div id="div3"></div>
+</body>
+</html>
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-containing-block-001-ref.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-containing-block-001-ref.html
new file mode 100644
index 000000000000..5df0b2462925
--- /dev/null
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-containing-block-001-ref.html
@@ -0,0 +1,37 @@
+<!doctype html>
+<html lang=en>
+  <head>
+    <meta charset=utf-8>
+    <title>CSS Reftest Reference</title>
+    <link rel="author" title="Yusuf Sermet" href="mailto:ysermet@mozilla.com">
+    <style>
+      rb,
+      rbc,
+      rt,
+      rtc {
+        background-color: yellow;
+        font-size: 2em;
+      }
+      rbc {
+        display: ruby-base-container;
+      }
+      .contained {
+        width: 50px;
+        height: 10px;
+        background-color: blue;
+        top: 0;
+        left: 0;
+        position: fixed;
+      }
+      .wrapper {
+        display: inline-block;
+      }
+    </style>
+  </head>
+  <body>
+    <div class="wrapper"><ruby><rt>&emsp;<div class="contained"></div></rt></ruby></div>
+    <div class="wrapper"><ruby><rtc>&emsp;<div class="contained"></div></rtc></ruby></div>
+    <div class="wrapper"><ruby><rb>&emsp;<div class="contained"></div></rb></ruby></div>
+    <div class="wrapper"><ruby><rbc>&emsp;<div class="contained"></div></rbc></ruby></div>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-containing-block-001.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-containing-block-001.html
new file mode 100644
index 000000000000..71764e18558a
--- /dev/null
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-containing-block-001.html
@@ -0,0 +1,41 @@
+<!doctype html>
+<html lang=en>
+  <head>
+    <meta charset=utf-8>
+    <title>CSS-contain test: paint containment on internal ruby elements.</title>
+    <link rel="author" title="Yusuf Sermet" href="mailto:ysermet@mozilla.com">
+    <link rel="help" href="http://www.w3.org/TR/css-containment-1/#containment-paint">
+    <link rel="match" href="contain-paint-ignored-cases-ruby-containing-block-001-ref.html">
+    <meta name="assert" content="Paint containment should not apply to ruby base, ruby base container, ruby text, and ruby text container. This test confirms contain:paint does not act as a containing block for fixed positioned descendants.">
+    <style>
+      rb,
+      rbc,
+      rt,
+      rtc {
+        contain: paint;
+        background-color: yellow;
+        font-size: 2em;
+      }
+      rbc {
+        display: ruby-base-container;
+      }
+      .contained {
+        width: 50px;
+        height: 10px;
+        background-color: blue;
+        top: 0;
+        left: 0;
+        position: fixed;
+      }
+      .wrapper {
+        display: inline-block;
+      }
+    </style>
+  </head>
+  <body>
+    <div class="wrapper"><ruby><rt>&emsp;<div class="contained"></div></rt></ruby></div>
+    <div class="wrapper"><ruby><rtc>&emsp;<div class="contained"></div></rtc></ruby></div>
+    <div class="wrapper"><ruby><rb>&emsp;<div class="contained"></div></rb></ruby></div>
+    <div class="wrapper"><ruby><rbc>&emsp;<div class="contained"></div></rbc></ruby></div>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-stacking-and-clipping-001-ref.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-stacking-and-clipping-001-ref.html
new file mode 100644
index 000000000000..02f7a406656c
--- /dev/null
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-stacking-and-clipping-001-ref.html
@@ -0,0 +1,52 @@
+<!doctype html>
+<html lang=en>
+  <head>
+    <meta charset=utf-8>
+    <title>CSS Reftest Reference</title>
+    <link rel="author" title="Yusuf Sermet" href="mailto:ysermet@mozilla.com">
+    <style>
+      div {
+        position: relative;
+      }
+      rbc {
+        display: ruby-base-container;
+      }
+      .contained {
+        z-index: 5;
+        width: 70px;
+        height: 10px;
+        background-color: blue;
+        margin-left: -25px;
+      }
+      .background {
+        display: inline-block;
+        background-color: yellow;
+        height: 50px;
+        width: 50px;
+        position: fixed;
+        z-index: 2;
+      }
+      .group {
+        display: inline-block;
+      }
+    </style>
+  </head>
+  <body>
+    <div class="group">
+      <div class="background"></div>
+      <ruby><rb>&emsp;<div class="contained"></div></rb></ruby>
+    </div>
+    <div class="group">
+      <div class="background"></div>
+      <ruby><rbc>&emsp;<div class="contained"></div></rbc></ruby>
+    </div>
+    <div class="group">
+      <div class="background"></div>
+      <ruby><rt>&emsp;<div class="contained"></div></rt></ruby>
+    </div>
+    <div class="group">
+      <div class="background"></div>
+      <ruby><rtc>&emsp;<div class="contained"></div></rtc></ruby>
+    </div>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-stacking-and-clipping-001.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-stacking-and-clipping-001.html
new file mode 100644
index 000000000000..1f1c147f94fa
--- /dev/null
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-stacking-and-clipping-001.html
@@ -0,0 +1,60 @@
+<!doctype html>
+<html lang=en>
+  <head>
+    <meta charset=utf-8>
+    <title>CSS-contain test: paint containment on internal ruby elements.</title>
+    <link rel="author" title="Yusuf Sermet" href="mailto:ysermet@mozilla.com">
+    <link rel="help" href="http://www.w3.org/TR/css-containment-1/#containment-paint">
+    <link rel="match" href="contain-paint-ignored-cases-ruby-stacking-and-clipping-001-ref.html">
+    <meta name="assert" content="Paint containment should not apply to ruby base, ruby base container, ruby text, and ruby text container. This test confirms that contain:paint does not create a stacking context and does not apply overflow clipping.">
+    <style>
+      div {
+        position: relative;
+      }
+      rb,
+      rbc,
+      rt,
+      rtc {
+        contain: paint;
+      }
+      rbc {
+        display: ruby-base-container;
+      }
+      .contained {
+        z-index: 5;
+        width: 70px;
+        height: 10px;
+        background-color: blue;
+        margin-left: -25px;
+      }
+      .background {
+        background-color: yellow;
+        height: 50px;
+        width: 50px;
+        position: fixed;
+        z-index: 2;
+      }
+      .group {
+        display: inline-block;
+      }
+    </style>
+  </head>
+  <body>
+    <div class="group">
+      <div class="background"></div>
+      <ruby><rb>&emsp;<div class="contained"></div></rb></ruby>
+    </div>
+    <div class="group">
+      <div class="background"></div>
+      <ruby><rbc>&emsp;<div class="contained"></div></rbc></ruby>
+    </div>
+    <div class="group">
+      <div class="background"></div>
+      <ruby><rt>&emsp;<div class="contained"></div></rt></ruby>
+    </div>
+    <div class="group">
+      <div class="background"></div>
+      <ruby><rtc>&emsp;<div class="contained"></div></rtc></ruby>
+    </div>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/reftest.list b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/reftest.list
index d503f7e5c663..7e762eceb77b 100644
--- a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/reftest.list
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/contain/reftest.list
@@ -9,5 +9,10 @@
 == contain-paint-containing-block-fixed-001.html contain-paint-containing-block-fixed-001-ref.html
 == contain-paint-formatting-context-float-001.html contain-paint-formatting-context-float-001-ref.html
 == contain-paint-formatting-context-margin-001.html contain-paint-formatting-context-margin-001-ref.html
+== contain-paint-ignored-cases-internal-table-001a.html contain-paint-ignored-cases-internal-table-001-ref.html
+== contain-paint-ignored-cases-internal-table-001b.html contain-paint-ignored-cases-internal-table-001-ref.html
+== contain-paint-ignored-cases-no-principal-box-001.html contain-paint-ignored-cases-no-principal-box-001-ref.html
+== contain-paint-ignored-cases-ruby-containing-block-001.html contain-paint-ignored-cases-ruby-containing-block-001-ref.html
+== contain-paint-ignored-cases-ruby-stacking-and-clipping-001.html contain-paint-ignored-cases-ruby-stacking-and-clipping-001-ref.html
 == contain-paint-stacking-context-001a.html contain-paint-stacking-context-001-ref.html
 == contain-paint-stacking-context-001b.html contain-paint-stacking-context-001-ref.html
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/shapes1/float-should-push-ref.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/shapes1/float-should-push-ref.html
new file mode 100644
index 000000000000..6a349fd359f5
--- /dev/null
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/shapes1/float-should-push-ref.html
@@ -0,0 +1,72 @@
+<!DOCTYPE HTML>
+<meta charset="utf-8">
+<title>Reference: Ensure shape-outside floats that don't cover their margin-rect affect layout properly</title>
+<link rel="author" title="Brad Werth" href="mailto:bwerth@mozilla.com">
+<link rel="author" title="Mozilla" href="http://www.mozilla.org/">
+
+<style>
+  body {
+    margin: 0px;
+    line-height: 1;
+  }
+
+  .container {
+    width: 300px;
+    height: 100px;
+    background: lightgray;
+  }
+
+  .too-wide {
+    display: inline-block;
+    width: 250px;
+    height: 20px;
+    background: lightblue;
+    clear: left;
+  }
+
+  .shape {
+    background: black;
+    width: 100px;
+    height: 100px;
+    float: left;
+  }
+
+  .spacer {
+    clear: left;
+    height: 30px;
+  }
+
+  .inset {
+    background: orange;
+  }
+
+  .polygon {
+    background: pink;
+  }
+
+  .image {
+    background: brown;
+  }
+
+</style>
+
+<p>All light blue bars should be pushed below the square floats, regardless of how those floats are defined.</p>
+
+<div class="container">
+<div class="shape inset">inset(1px) at top</div>
+<span class="too-wide"></span>
+</div>
+
+<div class="spacer"></div>
+
+<div class="container">
+<div class="shape polygon">polygon</div>
+<span class="too-wide"></span>
+</div>
+
+<div class="spacer"></div>
+
+<div class="container">
+<div class="shape image">image</div>
+<span class="too-wide"></span>
+</div>
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/shapes1/float-should-push.html b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/shapes1/float-should-push.html
new file mode 100644
index 000000000000..c6bcfe576b62
--- /dev/null
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/shapes1/float-should-push.html
@@ -0,0 +1,77 @@
+<!DOCTYPE HTML>
+<meta charset="utf-8">
+<title>Ensure shape-outside floats that don't cover their margin-rect affect layout properly</title>
+<link rel="author" title="Brad Werth" href="mailto:bwerth@mozilla.com">
+<link rel="author" title="Mozilla" href="http://www.mozilla.org/">
+<link rel="help" href="https://drafts.csswg.org/css-shapes-1/">
+<link rel="match" href="float-should-push-ref.html">
+<meta name="assert" content="Test that a too-wide inline block clear floats defined by shape-outside shapes that don't reach the top of the margin rect.">
+
+<style>
+  body {
+    margin: 0px;
+    line-height: 1;
+  }
+
+  .container {
+    width: 300px;
+    height: 100px;
+    background: lightgray;
+  }
+
+  .too-wide {
+    display: inline-block;
+    width: 250px;
+    height: 20px;
+    background: lightblue;
+  }
+
+  .shape {
+    background: black;
+    width: 100px;
+    height: 100px;
+    float: left;
+  }
+
+  .spacer {
+    clear: left;
+    height: 30px;
+  }
+
+  .inset {
+    background: orange;
+    shape-outside: inset(1px 0px 0px 0px);
+  }
+
+  .polygon {
+    background: pink;
+    shape-outside: polygon(0px 0px, 100px 0px, 100px 100px, 0px 100px);
+  }
+
+  .image {
+    background: brown;
+    shape-outside: linear-gradient(0deg, black, black 100%);
+  }
+
+</style>
+
+<p>All light blue bars should be pushed below the square floats, regardless of how those floats are defined.</p>
+
+<div class="container">
+<div class="shape inset">inset(1px) at top</div>
+<span class="too-wide"></span>
+</div>
+
+<div class="spacer"></div>
+
+<div class="container">
+<div class="shape polygon">polygon</div>
+<span class="too-wide"></span>
+</div>
+
+<div class="spacer"></div>
+
+<div class="container">
+<div class="shape image">image</div>
+<span class="too-wide"></span>
+</div>
diff --git a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/shapes1/reftest.list b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/shapes1/reftest.list
index cb4595acd60d..11b6a5a7d7e9 100644
--- a/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/shapes1/reftest.list
+++ b/testing/web-platform/tests/css/vendor-imports/mozilla/mozilla-central-reftests/shapes1/reftest.list
@@ -112,6 +112,8 @@
 
 # Tests of shape-outside layout behavior with too-wide inline elements
 == float-retry-push-circle.html float-retry-push-ref.html
+# The next test offsets a 250px wide element up to one pixel due to small offsets in gradient generation.
 == float-retry-push-image.html float-retry-push-ref.html
 == float-retry-push-inset.html float-retry-push-ref.html
 == float-retry-push-polygon.html float-retry-push-ref.html
+== float-should-push.html float-should-push-ref.html