chromium: add StartupWMClass to desktop file. Fixes #12433

pkgs/applications/networking/browsers/chromium/default.nix

@@ -57,6 +57,9 @@ let
       "x-scheme-handler/unknown"
     ];
     categories = "Network;WebBrowser";
+    extraEntries = ''
+      StartupWMClass=chromium-browser
+    '';
   };
 
   suffix = if channel != "stable" then "-" + channel else "";

pkgs/build-support/make-desktopitem/default.nix

@@ -10,6 +10,7 @@
 , mimeType ? ""
 , categories ? "Application;Other;"
 , startupNotify ? null
+, extraEntries ? ""
 }:
 
 stdenv.mkDerivation {
@@ -27,6 +28,7 @@ stdenv.mkDerivation {
     GenericName=${genericName}
     MimeType=${mimeType}
     Categories=${categories}
+    ${extraEntries}
     ${if startupNotify == null then ''EOF'' else ''
     StartupNotify=${startupNotify}
     EOF''}