Revert of gpu: introduce glCopySubTextureCHROMIUM

Revert of gpu: introduce glCopySubTextureCHROMIUM (patchset #4 id:80001 of https://codereview.chromium.org/864513004/)

Reason for revert:
This broke telemetry_unittests and content_browsertests on Mac (see issue 463439)

Original issue's description:
> gpu: introduce glCopySubTextureCHROMIUM
>
> Introduce glCopySubTextureCHROMIUM to support immutable texture as well as to
> optimize WebGL texSubImage2D(video | canvas).
>
> This CL changes gl_renderer to use glCopySubTextureCHROMIUM because the
> destination texture is immutable.
>
> TEST=GLCopyTextureCHROMIUMTest
> BUG=443151
>
> Committed: https://crrev.com/fac6a2d44323ad51429ee728e241fe22242f5ebd
> Cr-Commit-Position: refs/heads/master@{#318855}

TBR=sievers@chromium.org,piman@chromium.org,kbr@chromium.org,zmo@chromium.org,scherkus@chromium.org,dongseong.hwang@intel.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=443151
Committed: https://crrev.com/d8dd1b60962d234c304585028a36fd8896601420
Cr-Commit-Position: refs/heads/master@{#318858}

[ulan, 2015-03-03 10:12:01]

Created Revert of gpu: introduce glCopySubTextureCHROMIUM

[commit-bot: I haz the power, 2015-03-03 10:13:29]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/972833004/1

[commit-bot: I haz the power, 2015-03-03 10:14:42]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-03 10:15:21]

Patchset 1 (id:??) landed as
https://crrev.com/d8dd1b60962d234c304585028a36fd8896601420
Cr-Commit-Position: refs/heads/master@{#318858}