Bug 1064843 part 7 - Add backdrop pseudo-element and add related UA stylesheet. r=heycam

--HG--
extra : source : 79eadc4133fe81da5e01d9abbd0c5b1f95ae8d19

devtools/server/tests/mochitest/test_styles-applied.html

@@ -85,7 +85,7 @@ addTest(function inheritedSystemStyles() {
     ok(!applied[1].rule.parentStyleSheet.system, "Entry 1 should be a system style");
     is(applied[1].rule.type, 1, "Entry 1 should be a rule style");
 
-    is(applied.length, 11, "Should have 11 rules.");
+    is(applied.length, 12, "Should have 12 rules.");
   }).then(runNextTest));
 });
 

layout/inspector/tests/test_getCSSPseudoElementNames.html

@@ -12,6 +12,7 @@
   let expected = new Set([
     ":after",
     ":before",
+    ":backdrop",
     ":first-letter",
     ":first-line",
     ":-moz-color-swatch",

layout/style/nsCSSPseudoElementList.h

@@ -28,6 +28,8 @@
 CSS_PSEUDO_ELEMENT(after, ":after", CSS_PSEUDO_ELEMENT_IS_CSS2)
 CSS_PSEUDO_ELEMENT(before, ":before", CSS_PSEUDO_ELEMENT_IS_CSS2)
 
+CSS_PSEUDO_ELEMENT(backdrop, ":backdrop", 0)
+
 CSS_PSEUDO_ELEMENT(firstLetter, ":first-letter",
                    CSS_PSEUDO_ELEMENT_IS_CSS2 |
                    CSS_PSEUDO_ELEMENT_CONTAINS_ELEMENTS)

layout/style/ua.css

@@ -282,7 +282,6 @@
   left: 0 !important;
   right: 0 !important;
   bottom: 0 !important;
-  background: black;
   width: 100% !important;
   height: 100% !important;
   margin: 0 !important;
@@ -301,6 +300,18 @@
   -moz-top-layer: top !important;
 }
 
+*|*::backdrop {
+  -moz-top-layer: top !important;
+  display: block;
+  position: fixed;
+  top: 0; left: 0;
+  right: 0; bottom: 0;
+}
+
+*|*:-moz-full-screen:not(:root)::backdrop {
+  background: black;
+}
+
 /* XML parse error reporting */
 
 parsererror|parsererror {