Bug 1772609: Support cached hittesting on image maps r=Jamie

Differential Revision: https://phabricator.services.mozilla.com/D148556

accessible/generic/LocalAccessible.cpp

@@ -3248,6 +3248,22 @@ already_AddRefed<AccAttributes> LocalAccessible::BundleFieldsForCache(
           acc = acc->LocalParent();
         }
 
+        if (acc->IsImageMap()) {
+          // Layout doesn't walk image maps, so we do that
+          // manually here. We do this before adding the map itself
+          // so the children come earlier in the hittesting order.
+          for (uint32_t i = 0; i < acc->ChildCount(); i++) {
+            LocalAccessible* child = acc->LocalChildAt(i);
+            MOZ_ASSERT(child);
+            if (inViewAccs.EnsureInserted(child)) {
+              viewportCache.AppendElement(
+                  child->IsDoc()
+                      ? 0
+                      : reinterpret_cast<uint64_t>(child->UniqueID()));
+            }
+          }
+        }
+
         if (inViewAccs.EnsureInserted(acc)) {
           viewportCache.AppendElement(
               acc->IsDoc() ? 0 : reinterpret_cast<uint64_t>(acc->UniqueID()));

accessible/tests/browser/e10s/browser_caching_hittest.js

@@ -129,19 +129,16 @@ async function runTests(browser, accDoc) {
   const area = findAccessibleChildByID(accDoc, "area");
   await testChildAtPoint(dpr, 1, 1, area, area, area);
 
-  todo(
-    false,
-    "Test image maps. Their children are not in the layout tree. See bug 1772609"
+  info("Test image maps. Their children are not in the layout tree.");
+  const imgmap = findAccessibleChildByID(accDoc, "imgmap");
+  const theLetterA = imgmap.firstChild;
+  await hitTest(browser, imgmap, theLetterA, theLetterA);
+  await hitTest(
+    browser,
+    findAccessibleChildByID(accDoc, "container"),
+    imgmap,
+    theLetterA
   );
-  // const imgmap = findAccessibleChildByID(accDoc, "imgmap");
-  // const theLetterA = imgmap.firstChild;
-  // await hitTest(browser, imgmap, theLetterA, theLetterA);
-  // await hitTest(
-  //   browser,
-  //   findAccessibleChildByID(accDoc, "container"),
-  //   imgmap,
-  //   theLetterA
-  // );
 
   info("hit testing for element contained by zero-width element");
   const container2Input = findAccessibleChildByID(accDoc, "container2_input");