→XPCOM Shutdown Sequence: swap prior two columns for readability
<th>Step
<th>Description
<th>Main Event Queue
<th>Component Manager
<th>Main Event Queue
<th>Cross-module function calls
<th><tt>xpcom-shutdown</tt> notification
<td>Initial notification of xpcom shutdown... during this observer topic all primary modules should begin shutdown and should release any root references.