While investigating a separate issue, I noticed that I was hitting an assertion in the Cairo drawing layer because it was attempting to use an invalid HBITMAP created in the WebNodeHighlight::update method. The underlying issue was that the CreateDIBSection function was failing, because it was being requested to create a section of zero height.
I think the attached patch would be safe for the CoreGraphics and Cairo ports, but wanted to see if anyone knew of a reason why it would be bad to exit early in the case of a zero height (or zero width) paint region.
Created attachment 98790 [details]
Comment on attachment 98790 [details]
View in context: https://bugs.webkit.org/attachment.cgi?id=98790&action=review
> + ASSERT_WITH_MESSAGE(hbmp.get(), "::CreateDIBSection failed with error %lu", ::GetLastError());
No need for the .get() here.
Committed r89932: <http://trac.webkit.org/changeset/89932>