Extremely slow performance opening jquery-1.6.min.js

[peterflynn]

1. Make sure you have the brackets-scenario repo
2. Open the real_sites/PhoneGap_homepage folder
3. Click on js/jquery-1.6.min.js

Result: opening the JS file hangs brackets for ~15 seconds.

There's a secondary bug that's probably separable: after the above steps, the UI is extremely sluggish. Clicking to move the cursor or opening a menu takes 1-2 seconds every time. This issue goes away if you disable JSLint (closing the JSLint panel) -- even though JSLint seems to have no effect on how slow it is to initially open the file.

[peterflynn]

Unsurprisingly, this is not a regression -- still repros at least as far back as Sprint 5.

[gruehle]

CodeMirror doesn't handle long lines well. See:

https://github.com/marijnh/CodeMirror2/issues/397#issuecomment-4180204

[peterflynn]

Rats. Although that doesn't explain all the observed behavior -- e.g. I wonder why having the JSLint panel open in conjunction with that slows down not just CodeMirror operations, but also unrelated things like opening the menus.

[njx]

Marking "to user story"--this should turn into a performance story on the backlog.

[pthiess]

Moved to Trello, card 478

[peterflynn]

Looks like this may have been fixed by #1847