Heterogeneous DPI support on Linux

- VSCode Version: Code 1.19.1 (0759f77bb8d86658bc935a10a64f6182c5a1eeba, 2017-12-19T09:41:01.414Z) - OS Version: Linux x64 4.14.11-300.fc27.x86_64 Steps to Reproduce: 1. A Wayland desktop session on a multi-display setup with heterogeneous DPI scaling. Mine is a HiDPI laptop display scaled at 200% and an external monitor using 100% scaling, resulting in xwayland scaled at 100% on all displays. gnome-shell is the compositor. 2. Launch Visual Studio Code. 3. Move the IDE window between the displays. Like any other X11 application, Visual Studio Code cannot adapt to heterogeneous scaling. Wayland support, discussed in #1739, is needed to enable this. I feel that opening a new issue is justified by the problem described, which was not mentioned by the commenters on that issue. <!-- Launch with `code --disable-extensions` to check. --> Does this issue occur when all extensions are disabled?: Yes