Revert of "webgl: optimize webgl.texSubImage2D(video) path."

Revert of "webgl: optimize webgl.texSubImage2D(video) path." (patchset #3 id:40001 of https://codereview.chromium.org/1413833006/ )

Reason for revert:
Reverting this due to the security concerns piman raised, also it broke video related texture tests on Android.

Original issue's description:
> Reland of "webgl: optimize webgl.texSubImage2D(video) path."
>
> Original CL: https://codereview.chromium.org/1315323006/
> Revert: https://codereview.chromium.org/1418513016
>
> Reason for revert:
> Reverting to address webgl_conformance_tests break in:
> https://build.chromium.org/p/chromium.gpu/builders/Android%20Debug%20%28Nexus%209%29/builds/3534
>
> Reason for reland:
> There is a bug in glCopySubTextureCHROMIUM extension. GLES2DecoderImpl::DoCopySubTextureCHROMIUM/DoCompressedCopySubTextureCHROMIUM
> uses ValidForTexture to check dimensions of source texture. If the source
> texture is backed by GL Image, the decoder can report false positive error.
> This CL doesn't use Texture::ValidForTexture() for GL Image.
>
> TEST=WebglConformance.conformance_textures_video_tex_image_and_sub_image_2d_with_video_*
> BUG=349871, 504773, 549531
>
> Committed: https://crrev.com/7c26f04cf12c2c72fdab8e4764faf9305724c7ee
> Cr-Commit-Position: refs/heads/master@{#357100}

TBR=kbr@chromium.org,dalecurtis@chromium.org,philipj@opera.com,zmo@google.com,piman@chromium.org,dongseong.hwang@intel.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=349871, 504773, 549531
Committed: https://crrev.com/57d577a356a1ccc722dd5ef08e5481ee7a033c87
Cr-Commit-Position: refs/heads/master@{#357134}

[Zhenyao Mo, 2015-10-30 18:22:56]

Created Revert of "webgl: optimize webgl.texSubImage2D(video) path."

[commit-bot: I haz the power, 2015-10-30 18:23:57]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1420843005/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1420843005/1

[commit-bot: I haz the power, 2015-10-30 18:29:07]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-30 18:31:32]

Patchset 1 (id:??) landed as
https://crrev.com/57d577a356a1ccc722dd5ef08e5481ee7a033c87
Cr-Commit-Position: refs/heads/master@{#357134}