Support for Unity (Jumbo) builds
Unity (Jumbo) builds are a way to increase speed compilation for C/C++ projects.
The following article: A guide to unity builds by Viktor Kirilov describes the concept in detail.
Another article about Unity (Jumbo) builds: Support for Unity (Jumbo) Files in Visual Studio 2017 15.8.
See also the discussion on Google Chromium mailing list: Using unity builds (jumbo) for Chromium.