Bug 1681072 - Don't recurse into link if it is in more than one offset. r=MarcoZ

This is a safeguard for endless recursion in HyperTextIterator::NormalizeForward. Will catch similar corruptions found in bug 1682692.

Differential Revision: https://phabricator.services.mozilla.com/D99926

accessible/mac/HyperTextAccessibleWrap.mm

@@ -96,6 +96,13 @@ bool HyperTextIterator::NormalizeForward() {
 
     // If there is a link at this offset, mutate into it.
     if (link && link->IsHyperText()) {
+      if (mCurrentStartOffset > 0 &&
+          mCurrentContainer->LinkIndexAtOffset(mCurrentStartOffset) ==
+              mCurrentContainer->LinkIndexAtOffset(mCurrentStartOffset - 1)) {
+        MOZ_ASSERT_UNREACHABLE("Same link for previous offset");
+        return false;
+      }
+
       mCurrentContainer = link->AsHyperText();
       if (link->IsHTMLListItem()) {
         Accessible* bullet = link->AsHTMLListItem()->Bullet();