GN: Replace mojo/system.gni with forwarding groups

mojo/examples/surfaces_app/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//mojo/public/tools/bindings/mojom.gni")
-import("//mojo/system.gni")
 
 group("surfaces_app") {
   deps = [
     ":child_app",
     ":child_gl_app",
     ":parent_app",
   ]
 }
 
 # GYP version: mojo/mojo_examples.gypi:mojo_surfaces_app
 shared_library("parent_app") {
   output_name = "mojo_surfaces_app"
 
   deps = [
     ":bindings",
     ":util",
     "//base",
     "//cc",
     "//cc/surfaces",
     "//skia",
     "//ui/gfx",
     "//ui/gfx/geometry",
     "//mojo/application",
     "//mojo/common",
     "//mojo/environment:chromium",
+    "//mojo/public/c/system:for_shared_library",
     "//mojo/services/public/interfaces/geometry",
     "//mojo/services/public/cpp/geometry",
     "//mojo/services/public/interfaces/surfaces",
     "//mojo/services/public/cpp/surfaces",
-  ] + mojo_system_for_shared_library
+  ]
 
   sources = [
     "embedder.cc",
     "embedder.h",
     "surfaces_app.cc",
   ]
 }
 
 
 # GYP version: mojo/mojo_examples.gypi:mojo_surfaces_child_app
 shared_library("child_app") {
   output_name = "mojo_surfaces_child_app"
 
   deps = [
     ":bindings",
     ":util",
     "//base",
     "//cc",
     "//cc/surfaces",
     "//skia",
     "//ui/gfx",
     "//ui/gfx/geometry",
     "//mojo/application",
     "//mojo/common",
     "//mojo/environment:chromium",
+    "//mojo/public/c/system:for_shared_library",
     "//mojo/services/public/interfaces/geometry",
     "//mojo/services/public/cpp/geometry",
     "//mojo/services/public/interfaces/surfaces",
     "//mojo/services/public/cpp/surfaces",
-  ] + mojo_system_for_shared_library
+  ]
 
   sources = [
     "child_app.cc",
     "child_impl.cc",
     "child_impl.h",
   ]
 }
 
 # GYP version: mojo/mojo_examples.gypi:mojo_surfaces_child_gl_app
 shared_library("child_gl_app") {
   output_name = "mojo_surfaces_child_gl_app"
 
   deps = [
     ":bindings",
     ":util",
     "//base",
     "//cc",
     "//cc/surfaces",
     "//skia",
     "//ui/gfx",
     "//ui/gfx/geometry",
     "//mojo/common",
     "//mojo/application",
     "//mojo/environment:chromium",
     "//mojo/examples/sample_app:spinning_cube",
+    "//mojo/public/c/system:for_shared_library",
+    "//mojo/public/gles2:for_shared_library",
     "//mojo/services/public/interfaces/geometry",
     "//mojo/services/public/cpp/geometry",
     "//mojo/services/public/interfaces/surfaces",
     "//mojo/services/public/cpp/surfaces",
-  ] + mojo_system_for_shared_library + mojo_gles2_for_shared_library
+  ]
 
   sources = [
     "child_gl_app.cc",
     "child_gl_impl.cc",
     "child_gl_impl.h",
   ]
 }
 
 source_set("util") {
   deps = [
     "//cc",
     "//skia",
   ]
 
   sources = [
     "surfaces_util.cc",
     "surfaces_util.h",
   ]
 }
 
 # GYP version: mojo/mojo_examples.gypi:mojo_surfaces_app_bindings
 mojom("bindings") {
   deps = [
     "//mojo/services/public/interfaces/geometry",
     "//mojo/services/public/interfaces/surfaces",
   ]
 
   sources = [ "child.mojom" ]
 }