1. Go to http://us.battle.net/wow/en/game/dungeon-helper/
The Flash plugin on the right side of the page has a black background. It should instead have a transparent background (due to wmode=transparent).
This bug does not occur in WebKit1.
Here's another simple example: http://www.communitymx.com/content/source/E5141/wmodetrans.htm
I am having a surprisingly hard time writing a test case for this. I can't get transparent plugins to show up at all.
I'm going to land this without a test case. I filed bug 60169 to cover writing a test.
Created attachment 92244 [details]
Let transparent windowless plugins draw into a graphics context with an alpha channel
Committed r85753: <http://trac.webkit.org/changeset/85753>