gpu: Upgrade DEPTH_COMPONENT16 to DEPTH_COMPONENT24 if possible

gpu: Upgrade DEPTH_COMPONENT16 to DEPTH_COMPONENT24 if possible

Upgrade the DEPTH_COMPONENT16 render buffer storage format to
DEPTH_COMPONENT24 if the GLES implementation supports the OES_depth24
extension. This is done to improve content portability between desktop
and mobile, since we already do a similar mapping from DEPTH_COMPONENT16
to the unsized DEPTH_COMPONENT on desktop GL. This means that for
example WebGL content can end up relying on a higher precision depth
buffer even though it only requested DEPTH_COMPONENT16.

BUG=285400
TEST=http://www.khronos.org/registry/webgl/conformance-suites/1.0.1/webgl-conformance-tests.html on Nexus 4

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=224117

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=224509

[Ken Russell (switch to Gerrit), 2013-09-18 23:46:55]

Nice work. LGTM

Sorry about the failures on the GPU try bots. We think we've fixed the linux_gpu
server. I'll try to resubmit your patch to it.

[bajones, 2013-09-18 23:56:40]

LGTM too.

[commit-bot: I haz the power, 2013-09-19 10:06:43]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/skyostil@chromium.org/24079010/1

[commit-bot: I haz the power, 2013-09-19 13:04:14]

Change committed as 224117

[commit-bot: I haz the power, 2013-09-20 17:32:09]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/skyostil@chromium.org/24079010/26001

[commit-bot: I haz the power, 2013-09-20 22:50:39]

Change committed as 224509