Remove SWAP_PER_DRAW from GrGLGpu

This debug option was added back in 2011, and the code inside the
#define has not been compilable for many years.

Change-Id: I4366025da6e616f17f75dee14bced2809a90628f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/273038
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
1 file changed