The code to render QD plugins on offscreen GWorlds does not account for the position of the plugin when calculating the clipping rectangle for the QD window. This is apparent when using a Google Gadget like Bejeweled (URL attached) in an application that uses a WebKit view with an offscreen GWorld (i.e. not Safari). This was not previously noticed because many widgets/gadgets/Flash videos place the plugin content at (0,0); Google Gadgets on the other hand place a text label above the plugin.
Created attachment 16880 [details] Candidate patch for bug 15710; adds the origin to the clipping rect for offscreen GWorlds. This is a one-line change that should affect only applications that render to an offscreen GWorld (i.e. not Safari).
Comment on attachment 16880 [details] Candidate patch for bug 15710; adds the origin to the clipping rect for offscreen GWorlds. Looks fine, and I'm assuming you tested it in your project. r=me
Landed in r27148.