Only include the scene observatory test if the kernel file is present

Author: bdero

testing/dart/observatory/BUILD.gn

@@ -13,7 +13,10 @@ tests = [
 ]
 
 if (impeller_enable_3d) {
-  tests += [ "scene_reload_test.dart" ]
+  # This test is in a subdirectory to avoid the `run_test.py` glob by default.
+  # There is a special check to ensure the test's kernel file is present before
+  # it's added to the list of tests.
+  tests += [ "scene/scene_reload_test.dart" ]
 }
 
 foreach(test, tests) {

testing/dart/observatory/scene_reload_test.dart renamed to testing/dart/observatory/scene/scene_reload_test.dart

@@ -759,6 +759,14 @@ def gather_dart_tests(build_dir, test_filter):
   dart_observatory_tests = glob.glob(
       '%s/observatory/*_test.dart' % dart_tests_dir
   )
+  # Only include the 3D scene observatory test if the kernel file has been built.
+  # It'll only be built if Impeller Scene's framework integration is enabled.
+  dart_scene_observatory_tests = '%s/observatory/scene/scene_reload_test.dart' % dart_tests_dir
+  if os.path.isfile(
+      os.path.join(build_dir, 'gen',
+                   os.path.basename(dart_scene_observatory_tests) + '.dill')):
+    dart_observatory_tests += [dart_scene_observatory_tests]
+
   dart_tests = glob.glob('%s/*_test.dart' % dart_tests_dir)
 
   if 'release' not in build_dir: