Add an Android sample app for Telemetry tests.

tools/android/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.
 
 # Intermediate target grouping the android tools needed to run native
 # unittests and instrumentation test apks.
 #
 # GYP: //tools/android/android_tools.gyp:android_tools
 group("android_tools") {
   deps = [
@@ skipping 61 matching lines @@
   ]
 }
 
 # GYP: //tools/android/android_tools.gyp:audio_focus_grabber
 group("audio_focus_grabber") {
   testonly = true
   deps = [
     "//tools/android/audio_focus_grabber:audio_focus_grabber_apk",
   ]
 }
+
+# GYP: //tools/android/android_tools.gyp:push_apps_to_background
+group("push_apps_to_background") {
+  testonly = true
+  deps = [
+    "//tools/android/push_apps_to_background:push_apps_to_background_apk",
+  ]
+}