Now really backing out the offending mochitest, and also the patch I accidently checked in instead.

extensions/spellcheck/src/mozInlineSpellChecker.cpp

@@ -574,8 +574,19 @@ mozInlineSpellChecker::Init(nsIEditor *aEditor)
 nsresult mozInlineSpellChecker::Cleanup()
 {
   mNumWordsInSpellSelection = 0;
+  nsCOMPtr<nsISelection> spellCheckSelection;
+  nsresult rv = GetSpellCheckSelection(getter_AddRefs(spellCheckSelection));
+  if (NS_FAILED(rv)) {
+    // Ensure we still unregister event listeners (but return a failure code)
+    UnregisterEventListeners();
+  } else {
+    spellCheckSelection->RemoveAllRanges();
+
+    rv = UnregisterEventListeners();
+  }
   mEditor = nsnull;
-  return UnregisterEventListeners();
+
+  return rv;
 }
 
 // mozInlineSpellChecker::CanEnableInlineSpellChecking
@@ -699,16 +710,7 @@ mozInlineSpellChecker::SetEnableRealTimeSpell(PRBool aEnabled)
 {
   if (!aEnabled) {
     mSpellCheck = nsnull;
-    nsCOMPtr<nsISelection> spellCheckSelection;
-    nsresult rv = GetSpellCheckSelection(getter_AddRefs(spellCheckSelection));
-    if (NS_FAILED(rv)) {
-      // Ensure we still unregister event listeners (but return a failure code)
-      Cleanup();
-    } else {
-      spellCheckSelection->RemoveAllRanges();
-      rv = Cleanup();
-    }
-    return rv;
+    return Cleanup();
   }
 
   if (!mSpellCheck) {