Enable Chromium branch
Go to your Steam games list, right click on Garry's Mod and go to properties. Go to the Betas tab and click the drop down list, selecting [chromium -] to enable the Chromium branch of Garry's Mod
Missing map
To prevent the
"missing map" error you can preload the maps through our workshop collection.
Missing Textures
To prevent
Missing Textures and
Errors you can either download Counterstrike-Soucre and Half-Life 2, If you own them, or download it via the Content Collecction.