Add some simple HTMLViewer apptests.

mojo/services/html_viewer/BUILD.gn

Index: mojo/services/html_viewer/BUILD.gn
diff --git a/mojo/services/html_viewer/BUILD.gn b/mojo/services/html_viewer/BUILD.gn
index c609bb5e169066002b63a9c3b6563cf00c48ce79..823f740818906f03cdf7d773726eccd2c3a785ca 100644
--- a/mojo/services/html_viewer/BUILD.gn
+++ b/mojo/services/html_viewer/BUILD.gn
@@ -86,6 +86,7 @@ source_set("lib") {
     "//mojo/cc",
     "//mojo/common",
     "//mojo/converters/surfaces",
+    "//mojo/services/html_viewer/public/interfaces",
     "//mojo/services/network/public/cpp",
     "//mojo/services/network/public/interfaces",
     "//net",
@@ -185,3 +186,24 @@ test("tests") {
     "//base/test:run_all_unittests",
   ]
 }
+
+mojo_native_application("apptests") {
+  output_name = "html_viewer_apptests"
+  testonly = true
+
+  sources = [
+    "html_viewer_apptest.cc",
+  ]
+
+  deps = [
+    ":lib",
+    ":html_viewer",
+    #"//base" 
+    #"//base/test:test_config", 
+    "//mojo/application:test_support",
+    "//net:test_support",
+    "//testing/gtest",
+    "//third_party/mojo_services/src/http_server/public/cpp",
+    "//third_party/mojo_services/src/http_server/public/interfaces",
+  ]
+}