gpu: Avoid scissor test for glCopyTextureCHROMIUM if possible.

gpu: Avoid scissor test for glCopyTextureCHROMIUM if possible.

It's expensive to change scissor states, so avoid it if possible.

In addition, the meaning of (x|y)offset in DoCopySubTexture and
DoCopyTextureInternal are different. It's hard to understand. Make arguments of
DoCopyTextureInternal() same to them of DoCopySubTexture().

BUG=490889
Committed: https://crrev.com/fcf4d38c170e6aeafe4707b63bd1809d6eefb882
Cr-Commit-Position: refs/heads/master@{#333215}

[dshwang, 2015-06-05 13:49:56]

dongseong.hwang@intel.com changed reviewers:
+ piman@chromium.org, reveman@chromium.org, sievers@chromium.org

[dshwang, 2015-06-05 13:49:56]

piman, sievers, could you review this small optimization?
it's follow-up of reveman's https://codereview.chromium.org/1143373004/

[reveman, 2015-06-05 15:38:24]

lgtm

[no sievers, 2015-06-05 19:42:08]

lgtm

[piman, 2015-06-05 19:57:02]

lgtm

[dshwang, 2015-06-06 07:31:16]

thx for reviewing!

[dshwang, 2015-06-06 07:31:20]

The CQ bit was checked by dongseong.hwang@intel.com

[commit-bot: I haz the power, 2015-06-06 07:31:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1144103006/1

[commit-bot: I haz the power, 2015-06-06 07:34:15]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-06 07:34:59]

Patchset 1 (id:??) landed as
https://crrev.com/fcf4d38c170e6aeafe4707b63bd1809d6eefb882
Cr-Commit-Position: refs/heads/master@{#333215}