We get this error and no further DrawAndSwap happens. I'm investigating.

"glPostSubBufferCHROMIUM: command not supported by surface"

Seems like GLES2DecoderImpl::HandlePostSubBufferCHROMIUM is never called in non-viz mode at all. I'm not sure why what viz does differently that causes it to be called.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ff8129e257e2f9963302e76c69011d5400205793

commit ff8129e257e2f9963302e76c69011d5400205793
Author: Saman Sami <samans@chromium.org>
Date: Wed Jun 13 23:26:11 2018

Android/viz: Properly handle empty swaps

Android does not support partial swaps. Instead, when an empty swap
is requested we're supposed to commit overlay planes.

Bug:  850546 
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel
Change-Id: If77156732b4f43872855a8ad676c42a5e9842678
Reviewed-on: https://chromium-review.googlesource.com/1099266
Reviewed-by: kylechar <kylechar@chromium.org>
Commit-Queue: Saman Sami <samans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567042}
[modify] https://crrev.com/ff8129e257e2f9963302e76c69011d5400205793/components/viz/service/BUILD.gn
[modify] https://crrev.com/ff8129e257e2f9963302e76c69011d5400205793/components/viz/service/display_embedder/gl_output_surface.cc
[modify] https://crrev.com/ff8129e257e2f9963302e76c69011d5400205793/components/viz/service/display_embedder/gl_output_surface.h
[add] https://crrev.com/ff8129e257e2f9963302e76c69011d5400205793/components/viz/service/display_embedder/gl_output_surface_android.cc
[add] https://crrev.com/ff8129e257e2f9963302e76c69011d5400205793/components/viz/service/display_embedder/gl_output_surface_android.h
[modify] https://crrev.com/ff8129e257e2f9963302e76c69011d5400205793/components/viz/service/display_embedder/gpu_display_provider.cc