Bug 1415960 - Use flattened tree parent when returning GetContainerAccessible. r=Jamie

This fixes an inconsistency where CacheChildrenInSubtree uses the
flattened tree via DOM child iterators, but ProcessInvalidationList uses
GetContainerAccessible that doesn't currently use the flattened tree.

Differential Revision: https://phabricator.services.mozilla.com/D108980

accessible/generic/DocAccessible.cpp

@@ -1362,6 +1362,11 @@ LocalAccessible* DocAccessible::GetAccessibleOrContainer(
   return nullptr;
 }
 
+LocalAccessible* DocAccessible::GetContainerAccessible(nsINode* aNode) const {
+  return aNode ? GetAccessibleOrContainer(aNode->GetFlattenedTreeParentNode())
+               : nullptr;
+}
+
 LocalAccessible* DocAccessible::GetAccessibleOrDescendant(
     nsINode* aNode) const {
   LocalAccessible* acc = GetAccessible(aNode);

accessible/generic/DocAccessible.h

@@ -277,9 +277,7 @@ class DocAccessible : public HyperTextAccessibleWrap,
   /**
    * Return a container accessible for the given DOM node.
    */
-  LocalAccessible* GetContainerAccessible(nsINode* aNode) const {
-    return aNode ? GetAccessibleOrContainer(aNode->GetParentNode()) : nullptr;
-  }
+  LocalAccessible* GetContainerAccessible(nsINode* aNode) const;
 
   /**
    * Return an accessible for the given node if any, or an immediate accessible

accessible/tests/mochitest/treeupdate/test_shadow_slots.html

@@ -168,7 +168,18 @@
         (container, host) => {
           host.shadowRoot.getElementById("slot").remove();
       }, { SECTION: [{ SECTION: [{ name: "green"} ] }] });
+    }
 
+    function shadowProcessInvalidation() {
+      testAccessibleTree("shadowProcessInvalidation",
+      { SECTION: [{
+          SECTION: [{
+            SECTION: [{ TEXT_LEAF: { name: "Hello "} },
+                      { TEXT: [{ TEXT_LEAF: { name: "World"} }] },
+                      { PUSHBUTTON: { name: "World"} }]
+          }]
+        }]
+      });
     }
 
     async function doTest() {
@@ -202,6 +213,8 @@
 
       await shadowReassignDynamic_4();
 
+      shadowProcessInvalidation();
+
       SimpleTest.finish();
     }
 
@@ -462,6 +475,20 @@
     </script>
   </div>
 
+  <div id="shadowProcessInvalidation">
+    <template class="shadowtree">
+      <div id="shadowdiv">
+        <slot></slot>
+      </div>
+    </template>
+    <section class="host">Hello <span id="c">World</span><button aria-labelledby="c"></button></section>
+    <script>
+      document.querySelector("#shadowProcessInvalidation > .host")
+        .attachShadow({ mode: "open" })
+        .appendChild(document.querySelector("#shadowProcessInvalidation > .shadowtree").content.cloneNode(true));
+    </script>
+  </div>
+
   <div id="eventdump"></div>
 </body>
 </html>