Create native_viewport_service, don't build it into mojo_shell unless Android

mojo/services/native_viewport/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("//build/config/ui.gni")
 import("//mojo/system.gni")
 
-static_library("native_viewport") {
+shared_library("native_viewport") {
   output_name = "mojo_native_viewport"
 
   deps = [
+    ":lib",
+    "//mojo/services/public/interfaces/native_viewport",
+  ]
+  deps += mojo_system_for_shared_library
+
+  sources = [ "main.cc" ]
+}
+
+source_set("lib") {
+  deps = [
     "//base",
     "//cc/surfaces",
     "//mojo/common",
     "//mojo/environment:chromium",
     "//mojo/public/cpp/application:chromium",
     "//mojo/services/gles2",
     "//mojo/services/public/cpp/geometry",
     "//mojo/services/public/cpp/input_events",
     "//mojo/services/public/cpp/surfaces",
     "//mojo/services/public/interfaces/geometry",
@@ skipping 20 matching lines @@
   ]
 
   if (is_ios) {
     sources += [ "platform_viewport_stub.cc" ]
   }
 
   if (is_android) {
     deps += [ "//mojo:jni_headers" ]
   }
 
-  if (is_win) {
-    deps += [
-      # TODO(GYP)
-      # '../ui/platform_window/win/win_window.gyp:win_window',
-    ]
-  }
-
   if (use_x11) {
     sources += [ "platform_viewport_x11.cc" ]
     deps += [
       "//ui/events/platform/x11",
       "//ui/platform_window/x11",
     ]
   }
 
   if (use_ozone) {
     sources += [ "platform_viewport_ozone.cc" ]
   }
 }