Bug 1574428: IAccessible2_2::relationTargetsOfType: Support 0 for all targets and fix off-by-one error. r=MarcoZ

1. As per the spec, if maxTargets is 0, return all targets.
2. Where maxTargets > 0, fix the loop condition so it doesn't incorrectly fetch one more target than requested.

Differential Revision: https://phabricator.services.mozilla.com/D42446

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

accessible/windows/ia2/ia2Accessible.cpp

@@ -493,8 +493,9 @@ ia2Accessible::get_relationTargetsOfType(BSTR aType, long aMaxTargets,
   MOZ_ASSERT(!acc->IsProxy());
   Relation rel = acc->RelationByType(*relationType);
   Accessible* target = nullptr;
-  while ((target = rel.Next()) &&
-         static_cast<long>(targets.Length()) <= aMaxTargets) {
+  while (
+      (target = rel.Next()) &&
+      (aMaxTargets == 0 || static_cast<long>(targets.Length()) < aMaxTargets)) {
     targets.AppendElement(target);
   }