Make a mojo:apptests GN meta-target, add apptests.

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index b51ff78b2cea25e479887b0c2f2e40ef2a781863..818f28205620c342151b79c6b91c16aea0a500b3 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -684,6 +684,7 @@ group("gn_mojo_targets") {
       "//media/mojo/interfaces:interfaces_python",
       "//media/mojo/services:cdm_service",
       "//media/mojo:tests",
+      "//mojo:apptests",
       "//net/interfaces:interfaces_dart",
       "//net/interfaces:interfaces_python",
       "//third_party/mojo/src/mojo/edk/js/test:js_integration_tests",
@@ -698,12 +699,8 @@ group("gn_mojo_targets") {
       "//third_party/mojo_services/src/window_manager/public/interfaces:interfaces_python",
     ]
 
-    if (!is_debug) {
-      deps += [
-        "//mojo/services/html_viewer:apptests",
-        "//mojo/services/html_viewer:tests",
-        "//mojo/services/network:apptests",
-      ]
+    if (!is_component_build) {
+      deps += [ "//mojo/services/html_viewer:tests" ]
     }
   }
 }