Also, modify the affine test to share the test image with the glimage test. LGTM=nigeltao R=nigeltao CC=golang-codereviews https://golang.org/cl/164400043
Also, modify the affine test to share the test image with the glimage test. LGTM=nigeltao R=nigeltao CC=golang-codereviews https://golang.org/cl/164400043