This is not the best approach but it works for now. We basically pull the cg
context from gfxASurface and wrap a DrawTarget around it. In the end we'll need
to plumb the DrawTarget through more.
--HG--
rename : dom/ipc/PTabContext.ipdlh => dom/ipc/PContent.ipdl
extra : rebase_source : 49eac0354864ae9f2e7434b8b1efacc37d69fc23