WGL: Update the Renderer to own the native GL context. Adds a RendererWGL which owns the native WGL GL context. Adds a ContextWGL which owns the RendererWGL and communicates the native WGL context back to DisplayWGL for making current. BUG=angleproject:2464 Change-Id: Ideb11c164da2c304f860c544a56450d0ad8fafac Reviewed-on: https://chromium-review.googlesource.com/1038131 Commit-Queue: Geoff Lang <geofflang@chromium.org> Reviewed-by: Yuly Novikov <ynovikov@chromium.org>