GN: Mojo wget, sample_app, surfaces app and component build

mojo/examples/sample_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/system.gni")
+
+# GYP version: mojo/mojo_examples.gypi:mojo_sample_app
+shared_library("sample_app") {
+  output_name = "mojo_sample_app"
+
+  deps = [
+    "//mojo/public/cpp/application:main_standalone",
+    "//mojo/public/cpp/application:standalone",
+    "//mojo/public/cpp/bindings",
+    "//mojo/public/cpp/environment:standalone",
+    "//mojo/public/cpp/utility",
+    "//mojo/services/public/interfaces/geometry",
+    "//mojo/services/public/interfaces/native_viewport",
+  ] + mojo_system_for_shared_library + mojo_gles2_for_shared_library
+
+  sources = [
+    "gles2_client_impl.cc",
+    "gles2_client_impl.h",
+    "sample_app.cc",
+    "spinning_cube.cc",
+    "spinning_cube.h"
+  ]
+}