Revert of Import functionality for new GL backend

Revert of Import functionality for new GL backend (patchset #2 id:20001 of https://codereview.chromium.org/1185573003/)

Reason for revert:
breaking multiple builds. For example...

https://uberchromegw.corp.google.com/i/client.skia/builders/Test-Ubuntu-GCC-Golo-GPU-GT610-x86_64-Debug-ASAN/builds/667

Original issue's description:
> Import functionality for new GL backend
> 
> Brings in the following functionality:
> 
>   ARB_draw_instanced
>   ARB_instanced_arrays
>   NV_bindless_texture
>   EXT_direct_state_access
>   KHR_debug
> 
> Also cleans up some of the NVPR extension loading.
> 
> BUG=skia:
> 
> Committed: https://skia.googlesource.com/skia/+/202c4c75fb806f751cf796850bf67fe9793e0643

TBR=bsalomon@google.com,cdalton@nvidia.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Committed: https://skia.googlesource.com/skia/+/1fe1858a90532f4db578bffb97936742d39ede49

[djsollen, 2015-06-12 19:00:50]

Created Revert of Import functionality for new GL backend

[commit-bot: I haz the power, 2015-06-12 19:01:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1184863002/1

[commit-bot: I haz the power, 2015-06-12 19:01:20]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/1fe1858a90532f4db578bffb97936742d39ede49