Bug 1343886. Handle input or textarea elements having a non-textcontrol frame better. r=ehsan

MozReview-Commit-ID: FRzdvTLMAID

dom/html/nsTextEditorState.cpp

@@ -1553,11 +1553,13 @@ nsresult
 nsTextEditorState::GetSelectionRange(int32_t* aSelectionStart,
                                      int32_t* aSelectionEnd)
 {
-  MOZ_ASSERT(mBoundFrame,
-             "Caller didn't flush out frames and check for a frame?");
   MOZ_ASSERT(aSelectionStart);
   MOZ_ASSERT(aSelectionEnd);
 
+  if (!mBoundFrame) {
+    return NS_ERROR_FAILURE;
+  }
+
   // It's not clear that all the checks here are needed, but the previous
   // version of this code in nsTextControlFrame was doing them, so we keep them
   // for now.