Previously when pushing the GLES2 context with an onscreen framebuffer
it would just call bind_onscreen. This actually binds it with Cogl's
context so presumably the context isolation wasn't working properly.
This patch splits out bind_onscreen to have a second function called
bind_onscreen_with_context that explicitly takes the EGL context to
use. Cogl now uses this when pushing the GLES2 context.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
(cherry picked from commit 3653c5b10058a3f79900eb2644cb30f4cf1ca47e)
0edb848850