Revert of Improve tracking of bound FBOs in GrGLGpu. (patchset #17 id:320001 of https://codereview.chromium.org/949263002/)

Reason for revert:
Perf regression on win8 hd7700 gpu skps

Original issue's description:
> Improve tracking of bound FBOs in GrGLGpu.
>
> Committed: https://skia.googlesource.com/skia/+/d2ad8eb5801e2c8c0fa544a6a776bb46eedde2a0
>
> Committed: https://skia.googlesource.com/skia/+/b2af2d8b83ca4774c3b3bb1e49bc72605faa9589
>
> Committed: https://skia.googlesource.com/skia/+/0b70b86a7e9fda52ee7ebc1b9897eeaa09b9abef
>
> Committed: https://skia.googlesource.com/skia/+/6ba6fa15261be591f33cf0e5df7134e4fc6432ac
>
> Committed: https://skia.googlesource.com/skia/+/dc963b9264908f53650c40a97cff414101dd3e88
>
> Committed: https://skia.googlesource.com/skia/+/160f24ce0e8d6dd7ca80b78871e063d4f4609cfb

TBR=bsalomon@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/1009563003