After bug 700639, each time the debugger gets to a paused state the editor contents are refreshed, even though no change has occurred. The reason is that the XUL menulist we are now using needs to generate a change event every time a new script is loaded, which triggers the editor refresh. In the HTML select element case we could add options without triggering it, but I don't think that's possible now. But even if it were, the problem stems from the fact that when entering a paused state the debugger client sends a "scripts" protocol request to the server to retrieve any scripts the server is aware of. This is currently redundant, since the client also handles "newScript" notifications from the server each time a new script appears. The better fix would arguably be to remove the "scripts" request, as well as the "scriptsadded" and "scriptscleared" handlers from the debugger client.
The one time when a "scripts" request would be required is when opening the debugger UI. The debugger server may have already received a list of scripts in the page before the debugger UI was ready to handle such notifications, so it would be necessary to query once.
Created attachment 592710 [details] [diff] [review] Working patch Simple fix. I didn't include a test, because it looks complicated to write a proper one and it doesn't seem to make much sense for a one-liner, to be honest.