Adding missing manifest to gn-built app_list_demo

Many executables are missing embedded manifest files when built with gn.
This causes OS compatibility information to be omitted which can lead
to strange behavior. This adds a manifest to app_list_demo.exe.

BUG=602505

Review-Url: https://codereview.chromium.org/2027753002
Cr-Commit-Position: refs/heads/master@{#397042}

ui/app_list/BUILD.gn

@@ -244,6 +244,7 @@ if (toolkit_views) {
       ":test_support",
       "//base",
       "//build/config/sanitizers:deps",
+      "//build/win:default_exe_manifest",
       "//content",
       "//content/public/browser",
       "//skia",