Revert "Add method to sk_gpu_test::TestContext to automatically restore the previous context."

This reverts commit 5627d65146cb92624b682389e017d488872228c7.

Reason for revert: Google3

Original change's description:
> Add method to sk_gpu_test::TestContext to automatically restore the previous context.
> 
> The motivation for this is to allow a GM to create a GL context, do some some work in it, and then return to the context that was set when it was invoked.
> 
> Change-Id: Ie8496072a10f8f3ff36a08889e593a6ca961b61a
> Reviewed-on: https://skia-review.googlesource.com/70720
> Commit-Queue: Brian Salomon <bsalomon@google.com>
> Reviewed-by: Brian Osman <brianosman@google.com>

TBR=bsalomon@google.com,brianosman@google.com

Change-Id: Ifb79638c9d4500ca3be9a5be39a5ad78b20247c1
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/72981
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
21 files changed