ShareableBitmap currently always honors the alpha channel of its underlying data. This doesn't work well for use with APIs like GDI, which don't support alpha channels. (See bug 45567 comment 17 for one specific bug that this causes.)
We should have a way of specifying that a particular ShareableBitmap doesn't have an alpha channel.
In theory, this should make blitting into the window's backing store faster on Windows, since CG will be able to ignore the alpha channel entirely.
Created attachment 87426 [details]
Add a way to specify that a ShareableBitmap has no alpha channel
Committed r82442: <http://trac.webkit.org/changeset/82442>
Mac build fix
Committed r82445: <http://trac.webkit.org/changeset/82445>