When using unvirtualized contexts, DisplayWGL still creates a Renderer for
managing any internal GL resources such as emulated back buffers for
DXGISwapChainWindowSurfaceWGL or D3DTextureSurfaceWGL but also creates a new
Renderer for each GL context.  All created contexts share resources.

BUG=angleproject:2464

Change-Id: I945502514079368e062beef70bed49c61ed44403
Reviewed-on: https://chromium-review.googlesource.com/1097459
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>