Revert "Add a GpuGM class for GPU-only tests"

This reverts commit f5efa7890272bd7a3daf052af5ffa546903eb9a6.

Reason for revert: PreAbandon failures

Original change's description:
> Add a GpuGM class for GPU-only tests
> 
> Bug: skia:8731
> Change-Id: Ic81f21621c0183bb356601eb663fa1ee334bca55
> Reviewed-on: https://skia-review.googlesource.com/c/189134
> Reviewed-by: Brian Osman <brianosman@google.com>
> Reviewed-by: Mike Klein <mtklein@google.com>
> Commit-Queue: Chris Dalton <csmartdalton@google.com>

TBR=mtklein@google.com,brianosman@google.com,csmartdalton@google.com

Change-Id: Iab2a4323f077277445add18bb0e8c658d3bf0d2a
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:8731
Reviewed-on: https://skia-review.googlesource.com/c/190121
Reviewed-by: Chris Dalton <csmartdalton@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
23 files changed