fix: Use XDG_ACTIVATION_TOKEN in wayland when launched by other app (#43481)

When an electron app is launched by another app ensure that the
XDG_ACTIVATION_TOKEN env var is read and used for activation using
xdg_activation_v1 protocol.

shell/app/electron_main_delegate.cc

@@ -406,6 +406,11 @@ std::optional<int> ElectronMainDelegate::PreBrowserMain() {
   content::InitializeMojoCore();
 #if BUILDFLAG(IS_MAC)
   RegisterAtomCrApp();
+#endif
+#if BUILDFLAG(IS_LINUX)
+  // Set the global activation token sent as an environment variable.
+  auto env = base::Environment::Create();
+  base::nix::ExtractXdgActivationTokenFromEnv(*env);
 #endif
   return std::nullopt;
 }