Reason for revert:
Broke tests on Android, iOS, Mac and Windows.
Original issue's description:
> Make SkGLContext lifetime more well-defined
>
> Remove refcounting from SkGLContext.
>
> SkGLContext is expected to behave like GrContextFactory would own
> it, as implied by the GrContextFactory function.
>
> If it is refcounted, this does not hold.
>
> Also other use sites, such as in SkOSWindow_win (command buffer gl
> object), confirm the behavior. The object is explicitly owned and
> destroyed, not shared.
>
> Also fixes potential crashes from using GL context of an abandoned
> context.
>
> Also fixes potential crashes in DM/nanobench, if the GrContext lives
> longer than GLContext through internal refing of GrContext.
>
> Moves the non-trivial implementations from GrContextFactory.h to
> .cpp, just for consistency sake.
>
> Changes pathops_unittest.gyp. The pathops_unittest uses
> GrContextFactory, but did not link to its implementation. The reason
> they worked was that the implementation used (constructors, destructors)
> happened to be in the .h file.
>
> This works towards being able to use command buffer and NVPR from
> the SampleApp.
>
> BUG=skia:2992
> GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1511773005
>
> Committed: https://skia.googlesource.com/skia/+/830e012187f951d49d7e46e196ac8d1e653a25daTBR=bsalomon@google.com,kkinnunen@nvidia.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:2992
Review URL: https://codereview.chromium.org/1555053003
54e2ca5a23