*NOTE: Do not post confidential information in this bug report.*

What's the URL of the page containing the problem?
/r/##/diff/

What steps will reproduce the problem?
1. Create a review request with a lot of changes
2. Go to the diff page
3. Wait a *long* time

What is the expected output? What do you see instead?
The browser loads the whole page and then hangs.  It eventually will finish
up and start working again, but this may take a long time.  (Minutes even,
proportional to the size of the page)

What operating system are you using? What browser?
Windows XP, IE6

Please provide any additional information below.

I attached a debugger, and saw that it was looping in
htdocs/media/rb/js/csshover2.htc:getSelectedNodes().  It seems that for
many of the CSS rules, the tagName gets stripped down to an empty string,
which apparently makes it loop through the entire DOM tree.  For small
patches this is bearable, but it's unusable for large patches.

csshover2.htc is only loaded for IE6.  As I would expect, IE7 and Firefox3
don't show any issue.