GN: Replace mojo/system.gni with forwarding groups

mojo/examples/demo_launcher/BUILD.gn

Index: mojo/examples/demo_launcher/BUILD.gn
diff --git a/mojo/examples/demo_launcher/BUILD.gn b/mojo/examples/demo_launcher/BUILD.gn
index ebf78f13c60ec6e206a9cf462cedf6f20bd2d176..7c534b7a498a7fc9eefe7ae45b70b7d3303fc36a 100644
--- a/mojo/examples/demo_launcher/BUILD.gn
+++ b/mojo/examples/demo_launcher/BUILD.gn
@@ -3,7 +3,6 @@
 # found in the LICENSE file.
 
 import("//build/config/ui.gni")
-import("//mojo/system.gni")
 
 assert(use_aura)
 
@@ -22,9 +21,11 @@ shared_library("demo_launcher") {
     "//ui/gfx/geometry",
     "//ui/gl",
     "//mojo/application",
+    "//mojo/public/c/system:for_shared_library",
     "//mojo/public/cpp/bindings",
     "//mojo/public/cpp/utility",
+    "//mojo/public/gles2:for_shared_library",
     "//mojo/services/public/interfaces/geometry",
     "//mojo/services/public/interfaces/view_manager",
-  ] + mojo_system_for_shared_library + mojo_gles2_for_shared_library
+  ]
 }