Windows still uses OpenGL 1.1 to avoid the added complexity of linking
newer OpenGL APIs on that platform. MacOS has deprecated OpenGL and we
should eventually provide a Metal-based implementation on that platform.
- Windows: 10.0.17763.0 SDK is now required.
- Mac: 10.13 SDK is now required.
- Removed CefRequestContext::ResolveHostCached which is no longer supported by Chromium.