Merge pull request #1518 from MoonchildProductions/shadowdom-merge

Incremental shadowdom-merge

50 files changed, 343 insertions, 319 deletions

diff --git a/layout/reftests/bugs/1066554-1.html b/layout/reftests/bugs/1066554-1.html
index bb0a97f96..f4df207a1 100644
--- a/layout/reftests/bugs/1066554-1.html
+++ b/layout/reftests/bugs/1066554-1.html
@@ -7,15 +7,17 @@
   <script>
     function insertShadowSVG() {
       var x = document.getElementById("x");
-      x.createShadowRoot();
-      x.shadowRoot.innerHTML =
-        '<svg width="50px" height="10px"> \
-           <switch> \
-             <foreignObject width="50px" height="50px"> \
-               <div style="width: 100px; height: 10px; background: red;"></div> \
-             </foreignObject> \
-           </switch> \
-         </svg>';
+      if (x.createShadowRoot) {
+        x.createShadowRoot();
+        x.shadowRoot.innerHTML =
+          '<svg width="50px" height="10px"> \
+             <switch> \
+               <foreignObject width="50px" height="50px"> \
+                 <div style="width: 100px; height: 10px; background: red;"></div> \
+               </foreignObject> \
+             </switch> \
+           </svg>';
+      }
       document.documentElement.removeAttribute("class");
     }
     window.addEventListener("MozReftestInvalidate", insertShadowSVG, false);
diff --git a/layout/reftests/bugs/reftest.list b/layout/reftests/bugs/reftest.list
index d6f58a9c2..84d7f188f 100644
--- a/layout/reftests/bugs/reftest.list
+++ b/layout/reftests/bugs/reftest.list
@@ -1851,7 +1851,7 @@ test-pref(layout.css.grid.enabled,true) == 1053035-1-grid.html 1053035-1-ref.htm
 == 1062108-1.html 1062108-1-ref.html
 == 1062792-1.html 1062792-1-ref.html
 == 1062963-floatmanager-reflow.html 1062963-floatmanager-reflow-ref.html
-test-pref(dom.webcomponents.enabled,true) == 1066554-1.html 1066554-1-ref.html
+test-pref(dom.webcomponents.enabled,true) fails-if(stylo||styloVsGecko) == 1066554-1.html 1066554-1-ref.html
 == 1069716-1.html 1069716-1-ref.html
 == 1078262-1.html about:blank
 test-pref(layout.testing.overlay-scrollbars.always-visible,false) == 1081072-1.html 1081072-1-ref.html
diff --git a/layout/reftests/css-display/display-contents-shadow-dom-1-ref.html b/layout/reftests/css-display/display-contents-shadow-dom-1-ref.html
index f57822901..6e6dad233 100644
--- a/layout/reftests/css-display/display-contents-shadow-dom-1-ref.html
+++ b/layout/reftests/css-display/display-contents-shadow-dom-1-ref.html
@@ -45,8 +45,6 @@ span { color:blue; }
     <span style="color:green">R</span>
     <div></div>
     <b style="color:green">V</b>
-    <b style="color:green">W</b>
-    <b style="color:green">X</b>
     <!-- <b style="color:green">Y</b> -->
   </body>
 </html>
diff --git a/layout/reftests/css-display/display-contents-shadow-dom-1.html b/layout/reftests/css-display/display-contents-shadow-dom-1.html
index f5e49a192..6c0f297f9 100644
--- a/layout/reftests/css-display/display-contents-shadow-dom-1.html
+++ b/layout/reftests/css-display/display-contents-shadow-dom-1.html
@@ -51,8 +51,6 @@ div.after::after {content: " Y";}
     <div id="hostT" class="c">T</div>
     <div id="hostU"><span class="c">U</span></div>
     <div id="hostV" class="c" style="color:red"><b class="c" style="color:inherit">V</b></div>
-    <div id="hostW" class="c" style="color:red"><b class="c" style="color:inherit">W</b></div>
-    <span id="hostX" style="color:red"><b class="c" style="color:inherit">X</b></span>
     <!-- TODO(bug 1021572?) <div id="hostY" class="c" style="color:red"><b>Y</b></div> -->
 
    <script>
@@ -76,38 +74,40 @@ div.after::after {content: " Y";}
         return e;
       }
 
-      document.body.offsetHeight;
-
-      shadow("host1").innerHTML = '<content></content> c';
-      shadow("host2").innerHTML = 'a <content style="display:contents"></content> c';
-      shadow("host3").innerHTML = 'a <content style="display:contents"></content>';
-      shadow("host4").innerHTML = '<content style="display:contents"></content>';
-      shadow("host5").innerHTML = 'a <content style="display:contents"></content>';
-      shadow("host6").innerHTML = '<z style="color:blue; display:contents"><content></content></z> c';
-      shadow("host7").innerHTML = 'a <content style="display:contents"></content> c';
-      shadow("host8").innerHTML = 'a <z style="color:blue; display:contents"><content style="display:contents"></z></content>';
-      shadow("host9").innerHTML = '<content style="display:contents"></content>';
-      shadow("hostA").innerHTML = 'a <content style="display:contents"></content>';
-      shadow("hostB").innerHTML = 'a <content select=".c"></content> <content select=".b"></content> B';
-      shadow("hostC").innerHTML = 'A <content select=".c"></content> <content select=".b"></content> B';
-      shadow("hostD").innerHTML = 'A <content select=".c"></content> <content select=".b"></content> B <content select=".b"></content>';
-      shadow("hostE").innerHTML = 'A <content select=".c"></content> <content select=".b"></content> B';
-      shadow("hostF").innerHTML = '<content select=".c"></content> <content select=".b"></content> B';
-      shadow("hostG").innerHTML = '<content select=".b"></content>';
-      shadow("hostH").innerHTML = '<content select=".b"></content>';
-      shadow("hostI").innerHTML = 'A<content select=".b"></content>';
-      shadow("hostJ").innerHTML = 'A<content select=".b"></content>';
-      shadow("hostK").innerHTML = '<content select=".b"></content>';
-      shadow("hostL").innerHTML = '<content select=".b"></content>';
-      shadow("hostM").innerHTML = '<content select="b"></content><content select="i"></content>';
-      shadow("hostN").innerHTML = '<content select="b"></content><content select="i"></content>';
-      shadow("hostO").innerHTML = '<content select="b"></content><content select="i"></content>';
-      shadow("hostP").innerHTML = '<content select="b"></content><content select="i"></content>';
-      shadow("hostQ").innerHTML = '<content select="b"></content><content select="i"></content>';
-      shadow("hostR").innerHTML = '<content select="span"></content>';
-      shadow("hostW").innerHTML = '<z style="color:red"><content select="b"></content></z>';
-      shadow("hostX").innerHTML = '<z style="color:red"><content select="b"></content></z>';
-      // TODO(bug 1021572?) shadow("hostY").innerHTML = '<content select="b"><style scoped>:scope{color:green}</style></content>';
+      function run() {
+        document.body.offsetHeight;
+
+        shadow("host1").innerHTML = '<content></content> c';
+        shadow("host2").innerHTML = 'a <content style="display:contents"></content> c';
+        shadow("host3").innerHTML = 'a <content style="display:contents"></content>';
+        shadow("host4").innerHTML = '<content style="display:contents"></content>';
+        shadow("host5").innerHTML = 'a <content style="display:contents"></content>';
+        shadow("host6").innerHTML = '<z style="color:blue; display:contents"><content></content></z> c';
+        shadow("host7").innerHTML = 'a <content style="display:contents"></content> c';
+        shadow("host8").innerHTML = 'a <z style="color:blue; display:contents"><content style="display:contents"></z></content>';
+        shadow("host9").innerHTML = '<content style="display:contents"></content>';
+        shadow("hostA").innerHTML = 'a <content style="display:contents"></content>';
+        shadow("hostB").innerHTML = 'a <content select=".c"></content> <content select=".b"></content> B';
+        shadow("hostC").innerHTML = 'A <content select=".c"></content> <content select=".b"></content> B';
+        shadow("hostD").innerHTML = 'A <content select=".c"></content> <content select=".b"></content> B <content select=".b"></content>';
+        shadow("hostE").innerHTML = 'A <content select=".c"></content> <content select=".b"></content> B';
+        shadow("hostF").innerHTML = '<content select=".c"></content> <content select=".b"></content> B';
+        shadow("hostG").innerHTML = '<content select=".b"></content>';
+        shadow("hostH").innerHTML = '<content select=".b"></content>';
+        shadow("hostI").innerHTML = 'A<content select=".b"></content>';
+        shadow("hostJ").innerHTML = 'A<content select=".b"></content>';
+        shadow("hostK").innerHTML = '<content select=".b"></content>';
+        shadow("hostL").innerHTML = '<content select=".b"></content>';
+        shadow("hostM").innerHTML = '<content select="b"></content><content select="i"></content>';
+        shadow("hostN").innerHTML = '<content select="b"></content><content select="i"></content>';
+        shadow("hostO").innerHTML = '<content select="b"></content><content select="i"></content>';
+        shadow("hostP").innerHTML = '<content select="b"></content><content select="i"></content>';
+        shadow("hostQ").innerHTML = '<content select="b"></content><content select="i"></content>';
+        shadow("hostR").innerHTML = '<content select="span"></content>';
+        shadow("hostW").innerHTML = '<z style="color:red"><content select="b"></content></z>';
+        shadow("hostX").innerHTML = '<z style="color:red"><content select="b"></content></z>';
+        // TODO(bug 1021572?) shadow("hostY").innerHTML = '<content select="b"><style scoped>:scope{color:green}</style></content>';
+      }
 
       function tweak() {
         document.body.offsetHeight;
@@ -222,15 +222,18 @@ div.after::after {content: " Y";}
             shadow("hostT");
             shadow("hostU");
             shadow("hostV").innerHTML = '<z style="color:green"><content select="b"></content></z>';
-            shadow("hostW").innerHTML = '<z style="color:green"><content select="b"></content></z>';
-            shadow("hostX").innerHTML = '<z style="color:green"><content select="b"></content></z>';
 
             document.body.offsetHeight;
             document.documentElement.removeAttribute("class");
           },0);
       }
 
-      window.addEventListener("MozReftestInvalidate", tweak, false);
+      if (document.body.createShadowRoot) {
+        run();
+        window.addEventListener("MozReftestInvalidate", tweak, false);
+      } else {
+        document.documentElement.removeAttribute("class");
+      }
     </script>
   </body>
 </html>
diff --git a/layout/reftests/css-grid/reftest.list b/layout/reftests/css-grid/reftest.list
index 7c5e6be51..35e3140a8 100644
--- a/layout/reftests/css-grid/reftest.list
+++ b/layout/reftests/css-grid/reftest.list
@@ -248,10 +248,10 @@ asserts(0-10) == grid-fragmentation-015.html grid-fragmentation-015-ref.html # b
 == grid-fragmentation-dyn5-019.html grid-fragmentation-019-ref.html
 == grid-fragmentation-dyn1-020.html grid-fragmentation-020-ref.html
 == grid-fragmentation-dyn2-020.html grid-fragmentation-020-ref.html
-!= grid-fragmentation-dyn1-021.html grid-fragmentation-021-ref.html # bug 1251799
+== grid-fragmentation-dyn1-021.html grid-fragmentation-021-ref.html
 == grid-fragmentation-dyn2-021.html grid-fragmentation-021-ref.html
 == grid-fragmentation-dyn3-021.html grid-fragmentation-021-ref.html
-asserts(1-10) == grid-fragmentation-dyn4-021.html grid-fragmentation-021-ref.html # assertion related to bug 1251799 ?
+== grid-fragmentation-dyn4-021.html grid-fragmentation-021-ref.html
 == grid-fragmentation-dyn5-021.html grid-fragmentation-021-ref.html
 == grid-fragmentation-dyn2-022.html grid-fragmentation-007-ref.html
 == grid-fragmentation-dyn1-023.html grid-fragmentation-023-ref.html
diff --git a/layout/reftests/details-summary/reftest.list b/layout/reftests/details-summary/reftest.list
index e96581ad4..a972cf498 100644
--- a/layout/reftests/details-summary/reftest.list
+++ b/layout/reftests/details-summary/reftest.list
@@ -101,3 +101,7 @@ fuzzy(1,1) == mouse-click-twice-float-details.html float-details.html # Bug 1316
 == details-before.html single-summary.html
 == open-details-after.html open-single-summary.html
 == open-details-before.html open-single-summary.html
+
+# Move summary element
+== move-float-summary-to-different-details.html move-float-summary-to-different-details-ref.html
+== move-position-absolute-summary-to-different-details.html move-position-absolute-summary-to-different-details-ref.html
diff --git a/layout/reftests/forms/input/number/number-style-inheritance-ref.html b/layout/reftests/forms/input/number/number-style-inheritance-ref.html
new file mode 100644
index 000000000..00c8dba43
--- /dev/null
+++ b/layout/reftests/forms/input/number/number-style-inheritance-ref.html
@@ -0,0 +1,6 @@
+<!DOCTYPE html>
+<html>
+  <body>
+    <input type="text" style="width: 100px; text-decoration: underline;" value="1234">
+  </body>
+</html>
diff --git a/layout/reftests/forms/input/number/number-style-inheritance.html b/layout/reftests/forms/input/number/number-style-inheritance.html
new file mode 100644
index 000000000..b21ff1f1c
--- /dev/null
+++ b/layout/reftests/forms/input/number/number-style-inheritance.html
@@ -0,0 +1,6 @@
+<!DOCTYPE html>
+<html>
+  <body>
+    <input type="number" style="width: 100px; -moz-appearance: textfield; text-decoration: underline;" value="1234">
+  </body>
+</html>
diff --git a/layout/reftests/forms/input/number/reftest.list b/layout/reftests/forms/input/number/reftest.list
index ecf05ce15..bd07e274c 100644
--- a/layout/reftests/forms/input/number/reftest.list
+++ b/layout/reftests/forms/input/number/reftest.list
@@ -52,3 +52,6 @@ fuzzy-if(skiaContent,2,5) needs-focus == focus-handling.html focus-handling-ref.
 fuzzy(128,4) == number-reframe-anon-text-field.html number-reframe-anon-text-field-ref.html
 
 == pseudo-classes.html about:blank
+
+# Style inheritance:
+== number-style-inheritance.html number-style-inheritance-ref.html
diff --git a/layout/reftests/forms/legend/reftest.list b/layout/reftests/forms/legend/reftest.list
index 879835a59..03e25eb20 100644
--- a/layout/reftests/forms/legend/reftest.list
+++ b/layout/reftests/forms/legend/reftest.list
@@ -1,3 +1,3 @@
 == legend.html legend-ref.html
-fuzzy-if(skiaContent,1,7) pref(dom.webcomponents.enabled,true) == shadow-dom.html shadow-dom-ref.html
+#bug 1418002 fuzzy-if(skiaContent,1,7) pref(dom.webcomponents.enabled,true) == shadow-dom.html shadow-dom-ref.html
 == 1273433.html 1273433-ref.html
diff --git a/layout/reftests/forms/legend/shadow-dom.html b/layout/reftests/forms/legend/shadow-dom.html
index ad7babcf7..0f0a53665 100644
--- a/layout/reftests/forms/legend/shadow-dom.html
+++ b/layout/reftests/forms/legend/shadow-dom.html
@@ -48,17 +48,19 @@ div.after::after {content: " Y";}
         return e;
       }
 
-      document.body.offsetHeight;
+      function run() {
+        document.body.offsetHeight;
 
-      shadow("host1").innerHTML = '<content></content> c';
-      shadow("host2").innerHTML = 'a <content></content> c';
-      shadow("host3").innerHTML = 'a <content></content>';
-      shadow("host4").innerHTML = '<content></content>';
-      shadow("host5").innerHTML = 'a <content></content>';
-      shadow("host6").innerHTML = '<z style="color:blue; display:contents"><content></content></z> c';
-      shadow("host7").innerHTML = 'a <content select=".c"></content> <content select=".b"></content> B';
-      shadow("host8").innerHTML = 'A <content select=".c"></content> <content select=".b"></content> B';
-      shadow("host9").innerHTML = 'A <content select=".c"></content> <content select=".b"></content> B <content select=".b"></content>';
+        shadow("host1").innerHTML = '<content></content> c';
+        shadow("host2").innerHTML = 'a <content></content> c';
+        shadow("host3").innerHTML = 'a <content></content>';
+        shadow("host4").innerHTML = '<content></content>';
+        shadow("host5").innerHTML = 'a <content></content>';
+        shadow("host6").innerHTML = '<z style="color:blue; display:contents"><content></content></z> c';
+        shadow("host7").innerHTML = 'a <content select=".c"></content> <content select=".b"></content> B';
+        shadow("host8").innerHTML = 'A <content select=".c"></content> <content select=".b"></content> B';
+        shadow("host9").innerHTML = 'A <content select=".c"></content> <content select=".b"></content> B <content select=".b"></content>';
+      }
 
       function tweak() {
         document.body.offsetHeight;
@@ -105,7 +107,12 @@ div.after::after {content: " Y";}
           },0);
       }
 
-      window.addEventListener("MozReftestInvalidate", tweak, false);
+      if (document.body.createShadowRoot) {
+        run();
+        window.addEventListener("MozReftestInvalidate", tweak, false);
+      } else {
+        document.documentElement.removeAttribute("class");
+      }
     </script>
   </body>
 </html>
diff --git a/layout/reftests/mathml/shadow-dom-1.html b/layout/reftests/mathml/shadow-dom-1.html
index 547253a3c..bbf27069f 100644
--- a/layout/reftests/mathml/shadow-dom-1.html
+++ b/layout/reftests/mathml/shadow-dom-1.html
@@ -7,9 +7,11 @@
   <script>
     function insertShadowMathML() {
       var x = document.getElementById("x");
-      x.createShadowRoot();
-      x.shadowRoot.innerHTML =
-        '<math><msup><mi>X</mi><mi>X</mi></msup></math>';
+      if (x.createShadowRoot) {
+        x.createShadowRoot();
+        x.shadowRoot.innerHTML =
+          '<math><msup><mi>X</mi><mi>X</mi></msup></math>';
+      }
       document.documentElement.removeAttribute("class");
     }
     window.addEventListener("MozReftestInvalidate", insertShadowMathML, false);
diff --git a/layout/reftests/webcomponents/adjacent-insertion-points-1-ref.html b/layout/reftests/webcomponents/adjacent-insertion-points-1-ref.html
deleted file mode 100644
index 2c1f4e341..000000000
--- a/layout/reftests/webcomponents/adjacent-insertion-points-1-ref.html
+++ /dev/null
@@ -1,6 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<body>
-<div><span>Hello</span><span>World</span></div>
-</body>
-</html>
diff --git a/layout/reftests/webcomponents/adjacent-insertion-points-1.html b/layout/reftests/webcomponents/adjacent-insertion-points-1.html
deleted file mode 100644
index a8c6f983d..000000000
--- a/layout/reftests/webcomponents/adjacent-insertion-points-1.html
+++ /dev/null
@@ -1,17 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<head>
-  <script>
-    function tweak() {
-      var oldShadowRoot = document.getElementById('outer').createShadowRoot();
-      oldShadowRoot.innerHTML = 'World';
-
-      var youngShadowRoot = document.getElementById('outer').createShadowRoot();
-      youngShadowRoot.innerHTML = 'Hello<content></content><shadow></shadow>';
-    }
-  </script>
-</head>
-<body onload="tweak()">
-<div id="outer"></div>
-</body>
-</html>
diff --git a/layout/reftests/webcomponents/adjacent-insertion-points-2-ref.html b/layout/reftests/webcomponents/adjacent-insertion-points-2-ref.html
deleted file mode 100644
index 2c1f4e341..000000000
--- a/layout/reftests/webcomponents/adjacent-insertion-points-2-ref.html
+++ /dev/null
@@ -1,6 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<body>
-<div><span>Hello</span><span>World</span></div>
-</body>
-</html>
diff --git a/layout/reftests/webcomponents/adjacent-insertion-points-2.html b/layout/reftests/webcomponents/adjacent-insertion-points-2.html
deleted file mode 100644
index f90cb206b..000000000
--- a/layout/reftests/webcomponents/adjacent-insertion-points-2.html
+++ /dev/null
@@ -1,17 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<head>
-  <script>
-    function tweak() {
-      var oldShadowRoot = document.getElementById('outer').createShadowRoot();
-      oldShadowRoot.innerHTML = 'Hello';
-
-      var youngShadowRoot = document.getElementById('outer').createShadowRoot();
-      youngShadowRoot.innerHTML = '<shadow></shadow><content></content>World';
-    }
-  </script>
-</head>
-<body onload="tweak()">
-<div id="outer"></div>
-</body>
-</html>
diff --git a/layout/reftests/webcomponents/basic-insertion-point-1-ref.html b/layout/reftests/webcomponents/basic-insertion-point-1-ref.html
deleted file mode 100644
index 16f6afb28..000000000
--- a/layout/reftests/webcomponents/basic-insertion-point-1-ref.html
+++ /dev/null
@@ -1,8 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<body>
-<div>
-  <div style="border: 10px solid green">Hello</div>
-</div>
-</body>
-</html>
diff --git a/layout/reftests/webcomponents/basic-insertion-point-1.html b/layout/reftests/webcomponents/basic-insertion-point-1.html
deleted file mode 100644
index 727175ef3..000000000
--- a/layout/reftests/webcomponents/basic-insertion-point-1.html
+++ /dev/null
@@ -1,21 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<head>
-  <script>
-    function tweak() {
-      // div with style "border: 10px solid green"
-      var shadowDiv = document.createElement("div");
-      shadowDiv.style.border = "10px solid green";
-
-      var insertionPoint = document.createElement("content");
-      shadowDiv.appendChild(insertionPoint);
-
-      var shadowRoot = document.getElementById('outer').createShadowRoot();
-      shadowRoot.appendChild(shadowDiv);
-    }
-  </script>
-</head>
-<body onload="tweak()">
-<div id="outer">Hello</div>
-</body>
-</html>
diff --git a/layout/reftests/webcomponents/basic-insertion-point-2-ref.html b/layout/reftests/webcomponents/basic-insertion-point-2-ref.html
deleted file mode 100644
index 5e9213775..000000000
--- a/layout/reftests/webcomponents/basic-insertion-point-2-ref.html
+++ /dev/null
@@ -1,11 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<body>
-<div>
-  <div style="border: 10px solid green">
-    <span style="background-color: purple">Hello</span>
-    <span style="background-color: orange">World</span>
-  </div>
-</div>
-</body>
-</html>
diff --git a/layout/reftests/webcomponents/basic-insertion-point-2.html b/layout/reftests/webcomponents/basic-insertion-point-2.html
deleted file mode 100644
index 595edb471..000000000
--- a/layout/reftests/webcomponents/basic-insertion-point-2.html
+++ /dev/null
@@ -1,24 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<head>
-  <script>
-    function tweak() {
-      // div with style "border: 10px solid green"
-      var shadowDiv = document.createElement("div");
-      shadowDiv.style.border = "10px solid green";
-
-      var insertionPoint = document.createElement("content");
-      shadowDiv.appendChild(insertionPoint);
-
-      var shadowRoot = document.getElementById('outer').createShadowRoot();
-      shadowRoot.appendChild(shadowDiv);
-    }
-  </script>
-</head>
-<body onload="tweak()">
-<div id="outer">
-  <span style="background-color: purple">Hello</span>
-  <span style="background-color: orange">World</span>
-</div>
-</body>
-</html>
diff --git a/layout/reftests/webcomponents/basic-shadow-1.html b/layout/reftests/webcomponents/basic-shadow-1.html
index 944a594d2..8949dfc6d 100644
--- a/layout/reftests/webcomponents/basic-shadow-1.html
+++ b/layout/reftests/webcomponents/basic-shadow-1.html
@@ -9,7 +9,7 @@
       shadowDiv.style.height = "100px";
       shadowDiv.style.backgroundColor = "green";
 
-      var shadowRoot = document.getElementById('outer').createShadowRoot();
+      var shadowRoot = document.getElementById('outer').attachShadow({mode: 'open'});
       shadowRoot.appendChild(shadowDiv);
     }
   </script>
diff --git a/layout/reftests/webcomponents/basic-shadow-2.html b/layout/reftests/webcomponents/basic-shadow-2.html
index 587c47221..8e066997d 100644
--- a/layout/reftests/webcomponents/basic-shadow-2.html
+++ b/layout/reftests/webcomponents/basic-shadow-2.html
@@ -6,7 +6,7 @@
       var shadowDiv = document.createElement("div");
       shadowDiv.style.border = "10px solid green";
 
-      var shadowRoot = document.getElementById('outer').createShadowRoot();
+      var shadowRoot = document.getElementById('outer').attachShadow({mode: 'open'});
       shadowRoot.appendChild(shadowDiv);
 
       var orangeDiv = document.createElement("div");
diff --git a/layout/reftests/webcomponents/basic-shadow-3.html b/layout/reftests/webcomponents/basic-shadow-3.html
index 2ae53b5a9..3226c4baa 100644
--- a/layout/reftests/webcomponents/basic-shadow-3.html
+++ b/layout/reftests/webcomponents/basic-shadow-3.html
@@ -6,7 +6,7 @@
       var shadowDiv = document.createElement("div");
       shadowDiv.style.border = "10px solid green";
 
-      var shadowRoot = document.getElementById('outer').createShadowRoot();
+      var shadowRoot = document.getElementById('outer').attachShadow({mode: 'open'});
       shadowRoot.appendChild(shadowDiv);
 
       var orangeDiv = document.createElement("div");
diff --git a/layout/reftests/webcomponents/basic-shadow-4.html b/layout/reftests/webcomponents/basic-shadow-4.html
index 70f91773e..39dc51a9e 100644
--- a/layout/reftests/webcomponents/basic-shadow-4.html
+++ b/layout/reftests/webcomponents/basic-shadow-4.html
@@ -6,7 +6,7 @@
       var shadowDiv = document.createElement("div");
       shadowDiv.style.border = "10px solid green";
 
-      var shadowRoot = document.getElementById('outer').createShadowRoot();
+      var shadowRoot = document.getElementById('outer').attachShadow({mode: 'open'});
       shadowRoot.appendChild(shadowDiv);
 
       var orangeDiv = document.createElement("div");
diff --git a/layout/reftests/webcomponents/basic-shadow-element-1-ref.html b/layout/reftests/webcomponents/basic-shadow-element-1-ref.html
deleted file mode 100644
index a47b9362a..000000000
--- a/layout/reftests/webcomponents/basic-shadow-element-1-ref.html
+++ /dev/null
@@ -1,10 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<head>
-</head>
-<body>
-<div>
-  <div style="width:100px; height:100px; background-color:green"></div><div style="width:100px; height:100px; background-color:orange">Hello World</div>
-</div>
-</body>
-</html>
diff --git a/layout/reftests/webcomponents/basic-shadow-element-1.html b/layout/reftests/webcomponents/basic-shadow-element-1.html
deleted file mode 100644
index e51bd8b72..000000000
--- a/layout/reftests/webcomponents/basic-shadow-element-1.html
+++ /dev/null
@@ -1,19 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<head>
-  <script>
-    function tweak() {
-      var olderShadow = document.getElementById('outer').createShadowRoot();
-      olderShadow.innerHTML = '<div style="width:100px; height:100px; background-color: orange"><content></content></div>';
-
-      var youngerShadow = document.getElementById('outer').createShadowRoot();
-      youngerShadow.innerHTML = '<div style="width:100px; height:100px; background-color: green"></div><shadow>Hello World</shadow>';
-    }
-  </script>
-</head>
-<body onload="tweak()">
-<div id="outer">
-  <div style="width:300px; height:100px; background-color:red;"></div>
-</div>
-</body>
-</html>
diff --git a/layout/reftests/webcomponents/basic-slot-1-ref.html b/layout/reftests/webcomponents/basic-slot-1-ref.html
new file mode 100644
index 000000000..4f7418498
--- /dev/null
+++ b/layout/reftests/webcomponents/basic-slot-1-ref.html
@@ -0,0 +1,11 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <style>
+      body { color: green; }
+    </style>
+  </head>
+  <body>
+    This text should be green
+  </body>
+</html>
diff --git a/layout/reftests/webcomponents/basic-slot-1.html b/layout/reftests/webcomponents/basic-slot-1.html
new file mode 100644
index 000000000..b31f4c1c3
--- /dev/null
+++ b/layout/reftests/webcomponents/basic-slot-1.html
@@ -0,0 +1,6 @@
+<!DOCTYPE HTML>
+<html>
+  <body>
+    <slot style="color: green">This text should be green</slot>
+  </body>
+</html>
diff --git a/layout/reftests/webcomponents/basic-slot-2-ref.html b/layout/reftests/webcomponents/basic-slot-2-ref.html
new file mode 100644
index 000000000..d4d1b8c06
--- /dev/null
+++ b/layout/reftests/webcomponents/basic-slot-2-ref.html
@@ -0,0 +1,16 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <style>
+    div {
+      width: 100px;
+      height: 100px;
+      background: green;
+    }
+  </style>
+</head>
+<body>
+  <p>There should be a green box below.</p>
+  <div></div>
+</body>
+</html>
diff --git a/layout/reftests/webcomponents/basic-slot-2.html b/layout/reftests/webcomponents/basic-slot-2.html
new file mode 100644
index 000000000..3754ace20
--- /dev/null
+++ b/layout/reftests/webcomponents/basic-slot-2.html
@@ -0,0 +1,7 @@
+<!DOCTYPE HTML>
+<html>
+  <body>
+    <p>There should be a green box below.</p>
+    <slot style="display: block; width: 100px; height: 100px; background: green;"></slot>
+  </body>
+</html>
diff --git a/layout/reftests/webcomponents/basic-slot-3-ref.html b/layout/reftests/webcomponents/basic-slot-3-ref.html
new file mode 100644
index 000000000..54be54848
--- /dev/null
+++ b/layout/reftests/webcomponents/basic-slot-3-ref.html
@@ -0,0 +1,8 @@
+<!DOCTYPE HTML>
+<html>
+<body>
+<div>
+  <div style="color: green">This text should be green</div>
+</div>
+</body>
+</html>
diff --git a/layout/reftests/webcomponents/basic-slot-3.html b/layout/reftests/webcomponents/basic-slot-3.html
new file mode 100644
index 000000000..c00483fe2
--- /dev/null
+++ b/layout/reftests/webcomponents/basic-slot-3.html
@@ -0,0 +1,18 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <script>
+    function tweak() {
+      var slot = document.createElement("slot");
+      slot.style.color = "green";
+
+      var shadowRoot =
+        document.getElementById('outer').attachShadow({mode: 'open'});
+      shadowRoot.appendChild(slot);
+    }
+  </script>
+</head>
+<body onload="tweak()">
+<div id="outer">This text should be green</div>
+</body>
+</html>
diff --git a/layout/reftests/webcomponents/basic-slot-4.html b/layout/reftests/webcomponents/basic-slot-4.html
new file mode 100644
index 000000000..496a92651
--- /dev/null
+++ b/layout/reftests/webcomponents/basic-slot-4.html
@@ -0,0 +1,20 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <script>
+    function tweak() {
+      var slot = document.createElement("slot");
+      // The border shouldn't be visible, due to display: contents.
+      slot.style.border = "1px solid red";
+      slot.style.color = "green";
+
+      var shadowRoot =
+        document.getElementById('outer').attachShadow({mode: 'open'});
+      shadowRoot.appendChild(slot);
+    }
+  </script>
+</head>
+<body onload="tweak()">
+<div id="outer">This text should be green</div>
+</body>
+</html>
diff --git a/layout/reftests/webcomponents/cross-tree-selection-1.html b/layout/reftests/webcomponents/cross-tree-selection-1.html
index 1e4f02747..01e7317f2 100644
--- a/layout/reftests/webcomponents/cross-tree-selection-1.html
+++ b/layout/reftests/webcomponents/cross-tree-selection-1.html
@@ -3,6 +3,11 @@
 <head>
   <script>
     function tweak() {
+      if (!document.body.createShadowRoot) {
+        document.documentElement.className = "";
+        return;
+      }
+
       var host = document.getElementById("host");
       var shadow = host.createShadowRoot();
 
diff --git a/layout/reftests/webcomponents/dynamic-insertion-point-distribution-1.html b/layout/reftests/webcomponents/dynamic-insertion-point-distribution-1.html
index c57f72b37..8919a9c6a 100644
--- a/layout/reftests/webcomponents/dynamic-insertion-point-distribution-1.html
+++ b/layout/reftests/webcomponents/dynamic-insertion-point-distribution-1.html
@@ -5,9 +5,13 @@
   <body>
     <div id="host"></div>
     <script>
-      var host = document.getElementById("host");
-      var root = host.createShadowRoot();
-      root.innerHTML = 'a <content></content> c';
+      var host, root;
+
+      function run() {
+        host = document.getElementById("host");
+        root = host.createShadowRoot();
+        root.innerHTML = 'a <content></content> c';
+      }
 
       function tweak() {
         var span = document.createElement("span");
@@ -19,7 +23,12 @@
         document.documentElement.removeAttribute("class");
       }
 
-      window.addEventListener("MozReftestInvalidate", tweak, false);
+      if (document.body.createShadowRoot) {
+        run();
+        window.addEventListener("MozReftestInvalidate", tweak, false);
+      } else {
+        document.documentElement.className = "";
+      }
     </script>
   </body>
 </html>
diff --git a/layout/reftests/webcomponents/dynamic-insertion-point-distribution-2.html b/layout/reftests/webcomponents/dynamic-insertion-point-distribution-2.html
index 29a850e90..c58b9cfbd 100644
--- a/layout/reftests/webcomponents/dynamic-insertion-point-distribution-2.html
+++ b/layout/reftests/webcomponents/dynamic-insertion-point-distribution-2.html
@@ -5,9 +5,13 @@
   <body>
     <div id="host"></div>
     <script>
-      var host = document.getElementById("host");
-      var root = host.createShadowRoot();
-      root.innerHTML = "<span>a</span>";
+      var host, root;
+
+      function run() {
+        host = document.getElementById("host");
+        root = host.createShadowRoot();
+        root.innerHTML = "<span>a</span>";
+      }
 
       function tweak() {
         var span = document.createElement("span");
@@ -20,7 +24,12 @@
         document.documentElement.removeAttribute("class");
       }
 
-      window.addEventListener("MozReftestInvalidate", tweak, false);
+      if (document.body.createShadowRoot) {
+        run();
+        window.addEventListener("MozReftestInvalidate", tweak);
+      } else {
+        document.documentElement.className = "";
+      }
     </script>
   </body>
 </html>
diff --git a/layout/reftests/webcomponents/dynamic-shadow-element-1-ref.html b/layout/reftests/webcomponents/dynamic-shadow-element-1-ref.html
deleted file mode 100644
index a3b5150f6..000000000
--- a/layout/reftests/webcomponents/dynamic-shadow-element-1-ref.html
+++ /dev/null
@@ -1,10 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<head>
-</head>
-<body>
-<div>
-  <div style="background-color: green"><span>Hello</span><span> </span><span>World</span></div>
-</div>
-</body>
-</html>
diff --git a/layout/reftests/webcomponents/dynamic-shadow-element-1.html b/layout/reftests/webcomponents/dynamic-shadow-element-1.html
deleted file mode 100644
index 0142164a1..000000000
--- a/layout/reftests/webcomponents/dynamic-shadow-element-1.html
+++ /dev/null
@@ -1,23 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<head>
-  <script>
-    function tweak() {
-      var oldestShadow = document.getElementById('outer').createShadowRoot();
-      oldestShadow.innerHTML = 'Hello';
-
-      var olderShadow = document.getElementById('outer').createShadowRoot();
-
-      var youngerShadow = document.getElementById('outer').createShadowRoot();
-      youngerShadow.innerHTML = '<div style="background-color:green"><shadow></shadow></div>';
-
-      olderShadow.innerHTML = '<shadow></shadow> World';
-    }
-  </script>
-</head>
-<body onload="tweak()">
-<div id="outer">
-  <div style="width:300px; height:100px; background-color:red;"></div>
-</div>
-</body>
-</html>
diff --git a/layout/reftests/webcomponents/fallback-content-1.html b/layout/reftests/webcomponents/fallback-content-1.html
index ac3b5d02a..0bcd2abbd 100644
--- a/layout/reftests/webcomponents/fallback-content-1.html
+++ b/layout/reftests/webcomponents/fallback-content-1.html
@@ -8,13 +8,13 @@
       shadowDiv.style.border = "10px solid green";
 
       // Insertion point will match nothing and use fallback content.
-      var insertionPoint = document.createElement("content");
-      shadowDiv.appendChild(insertionPoint);
+      var slot = document.createElement("slot");
+      shadowDiv.appendChild(slot);
 
       // Append three nodes as children to use as fallback content.
-      insertionPoint.innerHTML = '<span style="background-color: orange">Hello</span> <span style="background-color: green">World</span>';
+      slot.innerHTML = '<span style="background-color: orange">Hello</span> <span style="background-color: green">World</span>';
 
-      var shadowRoot = document.getElementById('outer').createShadowRoot();
+      var shadowRoot = document.getElementById('outer').attachShadow({mode: 'open'});
       shadowRoot.appendChild(shadowDiv);
     }
   </script>
diff --git a/layout/reftests/webcomponents/input-transition-1.html b/layout/reftests/webcomponents/input-transition-1.html
index ede0fa40b..a4be5271b 100644
--- a/layout/reftests/webcomponents/input-transition-1.html
+++ b/layout/reftests/webcomponents/input-transition-1.html
@@ -5,19 +5,28 @@
   <body>
     <div id="host"></div>
     <script>
-      var host = document.getElementById("host");
-      var root = host.createShadowRoot();
-      root.innerHTML = '<style>input ~ div { background: red; transition: background 100ms; } input:checked ~ div { background: green; }</style><input id="one" type="checkbox"><div style="height: 50px; width: 50px;"></div>';
+      var host, root;
+
+      function run() {
+        host = document.getElementById("host");
+        root = host.createShadowRoot();
+        root.innerHTML = '<style>input ~ div { background: red; transition: background 100ms; } input:checked ~ div { background: green; }</style><input id="one" type="checkbox"><div style="height: 50px; width: 50px;"></div>';
+      }
 
       function tweak() {
-          var el = root.getElementById("one");
-          el.checked = true;
-          el.nextSibling.addEventListener("transitionend", function() {
-            document.documentElement.removeAttribute("class");
-          }, false);
+        var el = root.getElementById("one");
+        el.checked = true;
+        el.nextSibling.addEventListener("transitionend", function() {
+          setTimeout(()=>{document.documentElement.removeAttribute("class")}, 1000); // wait for the checkbox SVG image to load on Android
+        });
       }
 
-      window.addEventListener("MozReftestInvalidate", tweak, false);
+      if (document.body.createShadowRoot) {
+        run();
+        window.addEventListener("MozReftestInvalidate", tweak);
+      } else {
+        document.documentElement.className = "";
+      }
     </script>
   </body>
 </html>
diff --git a/layout/reftests/webcomponents/nested-insertion-point-1.html b/layout/reftests/webcomponents/nested-insertion-point-1.html
index 66892029a..3d0d92f0d 100644
--- a/layout/reftests/webcomponents/nested-insertion-point-1.html
+++ b/layout/reftests/webcomponents/nested-insertion-point-1.html
@@ -7,19 +7,20 @@
       var outerShadow = document.createElement("div");
       outerShadow.style.border = "10px solid green";
 
-      var outerInsertionPoint = document.createElement("content");
+      var outerInsertionPoint = document.createElement("slot");
       outerShadow.appendChild(outerInsertionPoint);
 
       // div with style "border: 10px solid orange"
       var innerShadow = document.createElement("div");
       innerShadow.style.border = "10px solid orange";
 
-      var innerInsertionPoint = document.createElement("content");
-      innerShadow.appendChild(innerInsertionPoint);
+      var slot = document.createElement("slot");
+      innerShadow.appendChild(slot);
 
-      outerShadow.createShadowRoot().appendChild(innerShadow);
+      outerShadow.attachShadow({mode: 'open'}).appendChild(innerShadow);
 
-      var shadowRoot = document.getElementById('outer').createShadowRoot();
+      var shadowRoot =
+        document.getElementById('outer').attachShadow({mode: 'open'});
       shadowRoot.appendChild(outerShadow);
     }
   </script>
diff --git a/layout/reftests/webcomponents/nested-shadow-element-1.html b/layout/reftests/webcomponents/nested-shadow-element-1.html
deleted file mode 100644
index cfaad3d49..000000000
--- a/layout/reftests/webcomponents/nested-shadow-element-1.html
+++ /dev/null
@@ -1,29 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<head>
-  <script>
-    function tweak() {
-      var olderShadow = document.getElementById('outer').createShadowRoot();
-      olderShadow.innerHTML = '<content></content><span>World</span>';
-
-      var youngerShadow = document.getElementById('outer').createShadowRoot();
-      youngerShadow.innerHTML = '<div id="shadowparent"><shadow id="youngshadow"><span>Hello</span></shadow></div>';
-
-      var shadowParent = youngerShadow.getElementById("shadowparent");
-      var nestedShadow = shadowParent.createShadowRoot();
-      nestedShadow.innerHTML = '<div style="background-color: green"><content></content></div>';
-
-      // Dynamically append a span to the shadow element in the younger ShadowRoot to make sure
-      // it is projected into the nested shadow.
-      var appendedSpan = document.createElement("span");
-      appendedSpan.textContent = ' ';
-      youngerShadow.getElementById("youngshadow").appendChild(appendedSpan);
-    }
-  </script>
-</head>
-<body onload="tweak()">
-<div id="outer">
-  <div style="width:300px; height:100px; background-color:red;"></div>
-</div>
-</body>
-</html>
diff --git a/layout/reftests/webcomponents/reframe-shadow-child-1.html b/layout/reftests/webcomponents/reframe-shadow-child-1.html
new file mode 100644
index 000000000..d953beb6d
--- /dev/null
+++ b/layout/reftests/webcomponents/reframe-shadow-child-1.html
@@ -0,0 +1,16 @@
+<!doctype html>
+<template id="tmpl">
+  <div style="display: table">
+    Some text
+    <span style="display: table-cell">something</span>
+    More text
+  </div>
+</template>
+<div id="host"></div>
+<script>
+  let shadowRoot = document.getElementById("host").attachShadow({mode: 'open'});
+  let tmpl = document.getElementById("tmpl");
+  shadowRoot.appendChild(document.importNode(tmpl.content, true));
+  document.body.offsetTop;
+  shadowRoot.firstElementChild.querySelector("span").remove();
+</script>
diff --git a/layout/reftests/webcomponents/reframe-shadow-child-2.html b/layout/reftests/webcomponents/reframe-shadow-child-2.html
new file mode 100644
index 000000000..0ebbe7433
--- /dev/null
+++ b/layout/reftests/webcomponents/reframe-shadow-child-2.html
@@ -0,0 +1,15 @@
+<!doctype html>
+<template id="tmpl">
+  <div style="display: block">
+    Some text
+    More text
+  </div>
+</template>
+<div id="host"></div>
+<script>
+  let shadowRoot = document.getElementById("host").attachShadow({mode: 'open'});
+  let tmpl = document.getElementById("tmpl");
+  shadowRoot.appendChild(document.importNode(tmpl.content, true));
+  document.body.offsetTop;
+  shadowRoot.firstElementChild.style.display = "table";
+</script>
diff --git a/layout/reftests/webcomponents/reftest.list b/layout/reftests/webcomponents/reftest.list
index beba21b18..6afbc2720 100644
--- a/layout/reftests/webcomponents/reftest.list
+++ b/layout/reftests/webcomponents/reftest.list
@@ -3,17 +3,17 @@ pref(dom.webcomponents.enabled,true) == basic-shadow-1.html basic-shadow-1-ref.h
 pref(dom.webcomponents.enabled,true) == basic-shadow-2.html basic-shadow-2-ref.html
 pref(dom.webcomponents.enabled,true) == basic-shadow-3.html basic-shadow-3-ref.html
 pref(dom.webcomponents.enabled,true) == basic-shadow-4.html basic-shadow-4-ref.html
-pref(dom.webcomponents.enabled,true) == basic-insertion-point-1.html basic-insertion-point-1-ref.html
-pref(dom.webcomponents.enabled,true) == basic-insertion-point-2.html basic-insertion-point-2-ref.html
-pref(dom.webcomponents.enabled,true) == adjacent-insertion-points-1.html adjacent-insertion-points-1-ref.html
-pref(dom.webcomponents.enabled,true) == adjacent-insertion-points-2.html adjacent-insertion-points-2-ref.html
 pref(dom.webcomponents.enabled,true) == fallback-content-1.html fallback-content-1-ref.html
 pref(dom.webcomponents.enabled,true) == remove-insertion-point-1.html remove-insertion-point-1-ref.html
-pref(dom.webcomponents.enabled,true) == nested-insertion-point-1.html nested-insertion-point-1-ref.html
-pref(dom.webcomponents.enabled,true) == basic-shadow-element-1.html basic-shadow-element-1-ref.html
-pref(dom.webcomponents.enabled,true) == nested-shadow-element-1.html nested-shadow-element-1-ref.html
-pref(dom.webcomponents.enabled,true) == update-dist-node-descendants-1.html update-dist-node-descendants-1-ref.html
+#bug 1421542 pref(dom.webcomponents.enabled,true) == nested-insertion-point-1.html nested-insertion-point-1-ref.html
+#bug 1421542 pref(dom.webcomponents.enabled,true) == update-dist-node-descendants-1.html update-dist-node-descendants-1-ref.html
 pref(dom.webcomponents.enabled,true) == input-transition-1.html input-transition-1-ref.html
-pref(dom.webcomponents.enabled,true) == dynamic-insertion-point-distribution-1.html dynamic-insertion-point-distribution-1-ref.html
+#bug 1421542 pref(dom.webcomponents.enabled,true) == dynamic-insertion-point-distribution-1.html dynamic-insertion-point-distribution-1-ref.html
 pref(dom.webcomponents.enabled,true) == dynamic-insertion-point-distribution-2.html dynamic-insertion-point-distribution-2-ref.html
 pref(dom.webcomponents.enabled,true) == remove-append-shadow-host-1.html remove-append-shadow-host-1-ref.html
+pref(dom.webcomponents.enabled,true) == basic-slot-1.html basic-slot-1-ref.html
+pref(dom.webcomponents.enabled,true) == basic-slot-2.html basic-slot-2-ref.html
+pref(dom.webcomponents.enabled,true) == basic-slot-3.html basic-slot-3-ref.html
+pref(dom.webcomponents.enabled,true) == basic-slot-4.html basic-slot-3-ref.html
+pref(dom.webcomponents.enabled,true) == basic-slot-5.html basic-slot-5-ref.html
+pref(dom.webcomponents.enabled,true) == basic-slot-6.html basic-slot-6-ref.html
diff --git a/layout/reftests/webcomponents/remove-append-shadow-host-1.html b/layout/reftests/webcomponents/remove-append-shadow-host-1.html
index 85161565e..1a752eba6 100644
--- a/layout/reftests/webcomponents/remove-append-shadow-host-1.html
+++ b/layout/reftests/webcomponents/remove-append-shadow-host-1.html
@@ -6,7 +6,7 @@
     <div id="container"><div id="host"></div></div>
     <script>
       var host = document.getElementById("host");
-      var root = host.createShadowRoot();
+      var root = host.attachShadow({mode: 'open'});
       root.innerHTML = 'inside shadow DOM';
 
       var container = document.getElementById("container");
diff --git a/layout/reftests/webcomponents/remove-insertion-point-1.html b/layout/reftests/webcomponents/remove-insertion-point-1.html
index 195673ca8..1b7588daf 100644
--- a/layout/reftests/webcomponents/remove-insertion-point-1.html
+++ b/layout/reftests/webcomponents/remove-insertion-point-1.html
@@ -8,15 +8,15 @@
       shadowDiv.style.border = "10px solid green";
 
       // Insertion point will match nothing and use fallback content.
-      var insertionPoint = document.createElement("content");
-      shadowDiv.appendChild(insertionPoint);
+      var slot = document.createElement("slot");
+      shadowDiv.appendChild(slot);
 
-      var shadowRoot = document.getElementById('outer').createShadowRoot();
+      var shadowRoot = document.getElementById('outer').attachShadow({mode: 'open'});
       shadowRoot.appendChild(shadowDiv);
 
       // Remove the insertion point from the ShadowRoot, "Hello" should no
       // longer be rendered.
-      shadowDiv.removeChild(insertionPoint);
+      shadowDiv.removeChild(slot);
     }
   </script>
 </head>
diff --git a/layout/reftests/webcomponents/style-sharing-across-shadow.html b/layout/reftests/webcomponents/style-sharing-across-shadow.html
new file mode 100644
index 000000000..b41cf7479
--- /dev/null
+++ b/layout/reftests/webcomponents/style-sharing-across-shadow.html
@@ -0,0 +1,22 @@
+<!doctype html>
+<style>
+  div { display: contents }
+</style>
+<div></div>
+<div></div>
+<script>
+  let divs = document.querySelectorAll('div');
+  divs[0].attachShadow({mode: 'open'}).innerHTML = `
+    <style>
+      * { color: green; }
+    </style>
+    <span>Should be green</span>
+  `;
+  divs[1].attachShadow({mode: 'open'}).innerHTML = `
+    <style>
+      * { color: initial; }
+      [foo] { }
+    </style>
+    <span>Should not be green</span>
+  `;
+</script>
diff --git a/layout/reftests/webcomponents/style-sharing.html b/layout/reftests/webcomponents/style-sharing.html
new file mode 100644
index 000000000..0a1e3c95c
--- /dev/null
+++ b/layout/reftests/webcomponents/style-sharing.html
@@ -0,0 +1,14 @@
+<!doctype html>
+<div id="host"></div>
+<script>
+  let root = host.attachShadow({mode: 'open'});
+  root.innerHTML = `
+    <style>
+      #test {
+        color: green;
+      }
+    </style>
+    <span id="test">Should be green</span>
+    <span id="test2">Should not be green</span>
+  `;
+</script>
diff --git a/layout/reftests/webcomponents/update-dist-node-descendants-1.html b/layout/reftests/webcomponents/update-dist-node-descendants-1.html
index e2dd4ebb7..3ba96594b 100644
--- a/layout/reftests/webcomponents/update-dist-node-descendants-1.html
+++ b/layout/reftests/webcomponents/update-dist-node-descendants-1.html
@@ -5,17 +5,25 @@
 <body>
 <div id="outer"><span id="distnode">text</span></div>
 <script>
-var shadowRoot = document.getElementById('outer').createShadowRoot();
-shadowRoot.innerHTML = '<div><content></content></div>';
 
-function tweak() {
-  var distNode = document.getElementById("distnode");
-  distNode.textContent = "Hello World";
-
-  document.documentElement.removeAttribute("class");
+function run() {
+  var shadowRoot = document.getElementById('outer').createShadowRoot();
+  shadowRoot.innerHTML = '<div><content></content></div>';
 }
 
-window.addEventListener("MozReftestInvalidate", tweak);
+  function tweak() {
+    var distNode = document.getElementById("distnode");
+    distNode.textContent = "Hello World";
+
+    document.documentElement.removeAttribute("class");
+	}
+
+if (document.body.createShadowRoot) {
+  run();
+  window.addEventListener("MozReftestInvalidate", tweak);
+} else {
+  document.documentElement.className = "";
+}
 </script>
 </body>
 </html>