chromium: Use upstream desktop entry

Upstream provides a much more featureful desktop entry file. If we use
that we take advantage of all of those features and don't have to maintain it
ourselves.

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

@@ -38,6 +38,25 @@ mkChromiumDerivation (base: rec {
       mkdir -vp "$logo_output_path"
       cp -v "$icon_file" "$logo_output_path/$packageName.png"
     done
+
+    # Install Desktop Entry
+    install -D chrome/installer/linux/common/desktop.template \
+      $out/share/applications/chromium-browser.desktop
+
+    substituteInPlace $out/share/applications/chromium-browser.desktop \
+      --replace "@@MENUNAME@@" "Chromium" \
+      --replace "@@PACKAGE@@" "chromium" \
+      --replace "Exec=/usr/bin/@@USR_BIN_SYMLINK_NAME@@" "Exec=chromium"
+
+    # Append more mime types to the end
+    sed -i '/^MimeType=/ s,$,x-scheme-handler/webcal;x-scheme-handler/mailto;x-scheme-handler/about;x-scheme-handler/unknown,' \
+      $out/share/applications/chromium-browser.desktop
+
+    # See https://github.com/NixOS/nixpkgs/issues/12433
+    sed -i \
+      -e '/\[Desktop Entry\]/a\' \
+      -e 'StartupWMClass=chromium-browser' \
+      $out/share/applications/chromium-browser.desktop
   '';
 
   passthru = { inherit sandboxExecutableName; };