Create an apptesting framework for dart.

services/dart/BUILD.gn

Index: services/dart/BUILD.gn
diff --git a/services/dart/BUILD.gn b/services/dart/BUILD.gn
index 0107f2c4f7f84846eb3f0ce60ab2e6f19ee9acc5..1beb12a5c092c0611dfb43fac8c6a4c1cd12f45c 100644
--- a/services/dart/BUILD.gn
+++ b/services/dart/BUILD.gn
@@ -135,27 +135,3 @@ mojo_native_application("dart_content_handler") {
     "//url:url",
   ]
 }
-
-mojo_native_application("dart_apptests") {
-  testonly = true
-
-  sources = [
-    "echo_apptest.cc",
-    "pingpong_apptest.cc",
-  ]
-
-  deps = [
-    "//base",
-    "//mojo/application",
-    "//mojo/application:test_support",
-    "//mojo/public/cpp/bindings",
-    "//mojo/public/cpp/system",
-    "//services/dart/test:echo_service_interface",
-    "//services/dart/test:pingpong_service_interface",
-  ]
-  data_deps = [
-    "//services/dart/test/echo",
-    "//services/dart/test/pingpong",
-    "//services/dart/test/pingpong_target",
-  ]
-}