Make mojo/application:test_support a group target.

mojo/application/BUILD.gn

Index: mojo/application/BUILD.gn
diff --git a/mojo/application/BUILD.gn b/mojo/application/BUILD.gn
index 8ecea3c5fbe87bcd5fe1df30330003c234047162..5ea3a25e0676148aaca11b55df63a8aec3ba6ded 100644
--- a/mojo/application/BUILD.gn
+++ b/mojo/application/BUILD.gn
@@ -35,7 +35,7 @@ source_set("content_handler") {
   ]
 }
 
-source_set("test_support") {
+source_set("test_support_source_set") {
   testonly = true
   sources = [
     "application_test_base_chromium.cc",
@@ -52,8 +52,16 @@ source_set("test_support") {
     "//third_party/mojo/src/mojo/public/cpp/system",
     "//testing/gtest",
   ]
+}
+
+# This group wraps the source_set above, so building any apptest that depends
+# on this target also builds this target's data_deps; see crbug.com/477104.
+group("test_support") {
+  testonly = true
+  public_deps = [
+    ":test_support_source_set",
+  ]
 
-  # TODO(msw): Any apptest target should build mojo shell; see crbug.com/477104.
   data_deps = []
   if (is_android) {
     data_deps += [ "//mojo/android" ]