Bug 1818404: Use HTMLLinkAccessible for SVG <a> elements. r=nlapre

This ensures that these are HyperTextAccessibles if they contain text, which prevents assertions and exposes formatting information.
It also gives these the correct role.

Differential Revision: https://phabricator.services.mozilla.com/D179409

accessible/base/nsAccessibilityService.cpp

@@ -1347,6 +1347,8 @@ LocalAccessible* nsAccessibilityService::CreateAccessible(
         // <g> can also contain <foreignObject>.
         newAcc =
             new EnumRoleHyperTextAccessible<roles::GROUPING>(content, document);
+      } else if (content->IsSVGElement(nsGkAtoms::a)) {
+        newAcc = new HTMLLinkAccessible(content, document);
       }
 
     } else if (content->IsMathMLElement()) {

accessible/tests/mochitest/role/test_svg.html

@@ -26,6 +26,7 @@
       testRole("path", ROLE_GRAPHIC);
       testRole("image", ROLE_GRAPHIC);
       testRole("image2", ROLE_GRAPHIC);
+      testRole("a", ROLE_LINK);
 
       SimpleTest.finish();
     }
@@ -85,6 +86,7 @@
     </image>
     <image x1="25" y1="110" width="50" height="20" id="image2"
            xlink:href="../moz.png" aria-label="hello"/>
+    <a href="#" id="a"><text>a</text></a>
   </svg>
 
 </body>

accessible/tests/mochitest/textattrs/test_svg.html

@@ -21,6 +21,10 @@
       const g = getNode("g");
       testTextAttrs(g, 0, {}, defAttrs, 0, 2);
 
+      const a = getNode("a");
+      const aDefAttrs = buildDefaultTextAttrs(a, "10pt");
+      testTextAttrs(a, 0, {}, aDefAttrs, 0, 1);
+
       SimpleTest.finish();
     }
 
@@ -41,6 +45,7 @@
       <title>g</title>
       <foreignobject>f2</foreignobject>
     </g>
+    <text><a href="#" id="a">a</a></text>
   </svg>
 
 </body>