1. Create a new web project
2. Unzip the attached "jquery-api.xml.zip" file
3. Add XML file to the new project
4. Open the XML file
5. Go to line 20781. It should start with "<html><![CDATA["
6. Delete lines 20781 to 20790.
The resulting behavior is intermittent. For me, the outline disappears and does not return. I can continue to edit the file, but the outline never returns. I have to close and re-open the file for the outline to return.
While trying to recreate this issue, I noticed my CPU went to 100%. I've attached a screenshot of the thread that appears to be causing this (see attached thread.png). Note that if you allow the thread to continue, it does eventually complete.