- wglSwapBuffers
- wglCreateContext
- wglMakeCurrent
These functions are needed by the OpenGL tutorial for Windows desktop

Bug: angleproject:3620
Change-Id: I699af63eca4a2c8aaf2c72278a580322410ac499
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1688499
Commit-Queue: Clemen Deng <clemendeng@google.com>
Reviewed-by: Geoff Lang <geofflang@chromium.org>