gpu: Measure texture uploads with glTexSubImage2D and glTexImage2D.

glTexImage2D and glTexSubImage2D could have different performance
properties.
With this patch we benchmark both of these upload techniques.

When using glTexSubImage2D the texture storage is specified with
glTexStorage2D when available, or glTexImage2D passing an empty pointer as data.

Trying to re-land this patch after it broke the perfbots (crbug.com/468748).

BUG=468748
Committed: https://crrev.com/e450ffd9dc792387272d5771fdec81639942655d
Cr-Commit-Position: refs/heads/master@{#321519}

[Daniele Castagna, 2015-03-20 04:21:29]

Patchset #1 (id:1) has been deleted

[Daniele Castagna, 2015-03-20 04:23:50]

dcastagna@chromium.org changed reviewers:
+ reveman@chromium.org

[reveman, 2015-03-20 04:29:22]

lgtm

[Daniele Castagna, 2015-03-20 04:31:27]

The CQ bit was checked by dcastagna@chromium.org

[commit-bot: I haz the power, 2015-03-20 04:31:40]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1027623002/20001

[commit-bot: I haz the power, 2015-03-20 05:11:18]

Committed patchset #1 (id:20001)

[commit-bot: I haz the power, 2015-03-20 05:12:04]

Patchset 1 (id:??) landed as
https://crrev.com/e450ffd9dc792387272d5771fdec81639942655d
Cr-Commit-Position: refs/heads/master@{#321519}