This reverts commit 13a8c4d8.

Reason for revert: Seems to have led to a flakier situation:

https://ci.chromium.org/p/chromium/builders/ci/Win10%20FYI%20Debug%20%28NVIDIA%29/3006
https://ci.chromium.org/p/chromium/builders/try/win-angle-rel/1231

Original change's description:
> Fix several WGL test failures.
> 
> SimpleOperationTest.ClearAndSwap/ES2_WGL failed when run in isolation,
> since getGLWindow()->hasError() would report a previous error,
> instead of result of swapBuffers().
> When running after an OPENGL test, swapBuffers() would clear
> the previous error, but that doesn't happen in isolation.
> 
> The previous error is from loading WGL functions, some of which are
> expected not to be present. Clear the error in GetProcAddressWithFallback,
> but verify that there is no error entering it.
> 
> This uncovers more errors in angle_perftests:
> DrawCallPerfBenchmark.Run/wgl
> DrawCallPerfBenchmark.Run/wgl_tex_change
> DrawCallPerfBenchmark.Run/wgl_vbo_change
> DrawElementsPerfBenchmark.Run/wgl_ushort
> They come from redundant calls when destroying a window. Fix this as well.
> 
> Several more errors where uncovered by debug prints, fix those, too.
> 
> Bug: angleproject:3153
> Change-Id: I559c098be9dcdfd3add83f045f745d190250b986
> Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1515602
> Commit-Queue: Yuly Novikov <ynovikov@chromium.org>
> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>

TBR=ynovikov@chromium.org,geofflang@chromium.org,syoussefi@chromium.org,jmadill@chromium.org

Change-Id: I095fadc0dd3a2c998c1dc86f3760184ae6fd7309
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: angleproject:3153
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1523527Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>