Re-enable single channel renderability for ANGLE ES2

Since the ANGLE-side fix has landed & been rolled into Skia we no longer need this workaround.

Change-Id: I9e6296976d53fc1c87232f918a5c0257201744bf
Reviewed-on: https://skia-review.googlesource.com/18583
Reviewed-by: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
1 file changed