This adds an extra test to test-gles2-context which renders to an FBO
and then checks that the orientation is correct once the texture is
rendered via Cogl. This should test the code path to flip the GLES2
rendering in Cogl.
The rendering is done in three different ways to test the various
state that needs flipping:
• Just renders two triangle strips, one at the top and one at the
bottom.
• Renders two full screen triangle strips, but each with a different
viewport to clip it to the top or the bottom.
• Clears the screen with two different colors and a scissor to either
the top or the bottom.
• Renders both quads twice with two different colors and two different
front face states.
Additionally the rendering is verified by calling glReadPixels to
check that the returned pixels are flipped correctly.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
(cherry picked from commit 5b097f9bc4a3eb316c6bf0d9fe8db00ff93bfe73)
d12399b823