Disallow drawing feedback loops.

Disallow drawing feedback loops.

BUG=421695
TEST=gpu_unittests, webgl_conformance_tests
R=bajones@chromium.org

Committed: https://crrev.com/f9a81360f858e271a0c95364172fdf90e2a5d240
Cr-Commit-Position: refs/heads/master@{#300019}

[Zhenyao Mo, 2014-10-14 23:09:59]

zmo@chromium.org changed reviewers:
+ kbr@chromium.org

[Zhenyao Mo, 2014-10-14 23:09:59]

Brandon, Ken, please review.

[Zhenyao Mo, 2014-10-14 23:10:56]

Tested with webgl conformance tests on Linux NVIDIA, no regression, and
https://www.khronos.org/registry/webgl/sdk/tests/conformance/renderbuffers/fe...
is passing after this CL.

[bajones, 2014-10-14 23:17:26]

lgtm

[Ken Russell (switch to Gerrit), 2014-10-16 21:08:30]

LGTM if the answer to this question is yes, and there's no major impact to
performance.

https://codereview.chromium.org/653203004/diff/1/gpu/command_buffer/service/g...
File gpu/command_buffer/service/gles2_cmd_decoder.cc (right):

https://codereview.chromium.org/653203004/diff/1/gpu/command_buffer/service/g...
gpu/command_buffer/service/gles2_cmd_decoder.cc:5763: bool
GLES2DecoderImpl::CheckDrawingFeedbackLoops() {
Have you checked any benchmarks -- e.g.
http://webglsamples.googlecode.com/hg/lots-o-objects/ ,
http://webglsamples.googlecode.com/hg/google-io/2011/ -- to see how much
overhead this new check adds? It could be significant.

[Zhenyao Mo, 2014-10-16 23:06:11]

On 2014/10/16 21:08:30, Ken Russell wrote:
> LGTM if the answer to this question is yes, and there's no major impact to
> performance.
> 
>
https://codereview.chromium.org/653203004/diff/1/gpu/command_buffer/service/g...
> File gpu/command_buffer/service/gles2_cmd_decoder.cc (right):
> 
>
https://codereview.chromium.org/653203004/diff/1/gpu/command_buffer/service/g...
> gpu/command_buffer/service/gles2_cmd_decoder.cc:5763: bool
> GLES2DecoderImpl::CheckDrawingFeedbackLoops() {
> Have you checked any benchmarks -- e.g.
> http://webglsamples.googlecode.com/hg/lots-o-objects/ ,
> http://webglsamples.googlecode.com/hg/google-io/2011/ -- to see how much
> overhead this new check adds? It could be significant.

Tested with the above suggested two demos plus WebGL Aquarium, no visible perf
differences.  Landing this.

[Zhenyao Mo, 2014-10-16 23:06:16]

The CQ bit was checked by zmo@chromium.org

[commit-bot: I haz the power, 2014-10-16 23:07:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/653203004/1

[commit-bot: I haz the power, 2014-10-17 00:06:22]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-10-17 00:06:54]

Patchset 1 (id:??) landed as
https://crrev.com/f9a81360f858e271a0c95364172fdf90e2a5d240
Cr-Commit-Position: refs/heads/master@{#300019}