Add an icon for SkyDemo (required by the play store)

sky/apk/demo/BUILD.gn

 # Copyright 2015 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.
 
 assert(is_android)
 
 import("//build/config/android/config.gni")
 import("//build/config/android/rules.gni")
 import("//sky/apk/rules.gni")
 
@@ skipping 13 matching lines @@
     "//sky/services/sensors:interfaces_java",
     "//sky/shell:java",
   ]
 }
 
 sky_apk("demo") {
   apk_name = "SkyDemo"
   android_manifest = "AndroidManifest.xml"
   deps = [
     ":java",
+    ":demo_resources",
   ]
 }
+
+android_resources("demo_resources") {
+  resource_dirs = [ "res" ]
+  android_manifest = "AndroidManifest.xml"
+}