Bug 1357100 - change implicit val for aria-level on a heading to 2 r=Jamie

Differential Revision: https://phabricator.services.mozilla.com/D35616

--HG--
extra : moz-landing-system : lando

accessible/generic/Accessible.cpp

@@ -1168,7 +1168,14 @@ GroupPos Accessible::GroupPosition() {
   // Calculate group level if ARIA is missed.
   if (groupPos.level == 0) {
     int32_t level = GetLevelInternal();
-    if (level != 0) groupPos.level = level;
+    if (level != 0) {
+      groupPos.level = level;
+    } else {
+      const nsRoleMapEntry* role = this->ARIARoleMap();
+      if (role && role->Is(nsGkAtoms::heading)) {
+        groupPos.level = 2;
+      }
+    }
   }
 
   // Calculate position in group and group size if ARIA is missed.
@@ -1940,7 +1947,8 @@ void Accessible::AppendTextTo(nsAString& aText, uint32_t aStartOffset,
 
 void Accessible::Shutdown() {
   // Mark the accessible as defunct, invalidate the child count and pointers to
-  // other accessibles, also make sure none of its children point to this parent
+  // other accessibles, also make sure none of its children point to this
+  // parent
   mStateFlags |= eIsDefunct;
 
   int32_t childCount = mChildren.Length();

accessible/tests/mochitest/attributes/test_obj_group.html

@@ -211,6 +211,7 @@
       testGroupAttrs("h4", 0, 0, 4);
       testGroupAttrs("h5", 0, 0, 5);
       testGroupAttrs("h6", 0, 0, 6);
+      testGroupAttrs("ariaHeadingNoLevel", 0, 0, 2);
       // No child item counts or "hierarchical" flag for parent of headings
       testAbsentAttrs("headings", {"child-item-count": "", "hierarchical": ""});
 
@@ -487,6 +488,7 @@
     <h4 id="h4">heading4</h4>
     <h5 id="h5">heading5</h5>
     <h6 id="h6">heading6</h6>
+    <div id="ariaHeadingNoLevel" role="heading">ariaHeadingNoLevel</div>
   </div>
 
   <ul id="combo1" role="combobox">Password