Add some simple HTMLViewer apptests.

mojo/application/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.
 
 # GYP version: mojo/mojo_base.gyp:mojo_application_chromium
 source_set("application") {
   sources = [
     "application_runner_chromium.cc",
     "application_runner_chromium.h",
   ]
@@ skipping 12 matching lines @@
   testonly = true
   sources = [
     "application_test_main_chromium.cc",
   ]
 
   public_deps = [
     "//third_party/mojo/src/mojo/public/cpp/application:test_support",
   ]
   deps = [
     "//base",
+    "//base/test:test_support",
   ]
 }