Bug 1330966 - Add an ACCESSIBILITY guard around DocAccessibleParent usage in TabParent.cpp to fix --disable-accessibility bustage. r=dbolter

--HG--
extra : rebase_source : 76f36b70f0b135e947047f276442b612a0bf30b0

dom/ipc/TabParent.cpp

@@ -359,9 +359,11 @@ TabParent::DestroyInternal()
 
   RemoveWindowListeners();
 
+#ifdef ACCESSIBILITY
   if (a11y::DocAccessibleParent* tabDoc = GetTopLevelDocAccessible()) {
     tabDoc->Destroy();
   }
+#endif
 
   // If this fails, it's most likely due to a content-process crash,
   // and auto-cleanup will kick in.  Otherwise, the child side will