Hardware accelerated off-screen rendering #506

CEF supports hardware-accelerated off-screen rendering by enabling shared_texture_enabled via WindowInfo and passing --off-screen-rendering-enabled --shared-texture-enabled as arguments.

• https://bitbucket.org/chromiumembedded/cef/pull-requests/734
• https://github.com/chromiumembedded/cef/blob/2c411892e273c564dfb6650dcee8fea458849178/include/cef_render_handler.h#L151-L173.

Unfortunately, Java CEF lacks bindings for OnAcceleratedPaint, meaning we cannot make use of this feature.