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The WGL path hasn't been used in the last many years and
shouldn't be used in the future since ANGLE provides an EGL
implementation on top of D3D or GL depending on what's available.

Remove all WGL support code since it isn't needed anymore.

Bug: chromium:1133372
Change-Id: I1c23f3b17682082e43d7c6072c085a94735e4cf8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2434341
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#811831}