Add dart:sky.internals and dart:sky_builtin_natives to Sky sdk_ext

mojo/public/dart/rules.gni

Index: mojo/public/dart/rules.gni
diff --git a/mojo/public/dart/rules.gni b/mojo/public/dart/rules.gni
index 21f4283085341058275f97de7e65f688d66558fb..ffe1734fa6c0ed735e59616bcad20ecce2990d84 100644
--- a/mojo/public/dart/rules.gni
+++ b/mojo/public/dart/rules.gni
@@ -224,6 +224,9 @@ template("dartzip_packaged_application") {
 #   sdk_ext_directory (optional)
 #       Directory containing sdk-ext .dart sources.
 #
+#   sdk_ext_files (optional)
+#       List of sources to include in sdk-ext.
+#
 template("dart_pkg") {
   if (defined(invoker.pkg_dir)) {
     pubspec_yaml_path = rebase_path("pubspec.yaml", "", invoker.pkg_dir)
@@ -276,6 +279,11 @@ template("dart_pkg") {
       sdk_ext_directory += [ invoker.sdk_ext_directory ]
     }
 
+    sdk_ext_files = []
+    if (defined(invoker.sdk_ext_files)) {
+      sdk_ext_files += invoker.sdk_ext_files
+    }
+
     script = rebase_path("mojo/public/tools/dart_pkg.py", ".", mojo_sdk_root)
     outputs = [
       stamp_file,
@@ -313,6 +321,7 @@ template("dart_pkg") {
              "--package-sources",
            ] + rebase_path(sources) + [ "--mojom-sources" ] +
            rebase_path(mojom_sources, "", mojo_sdk_root) +
-           [ "--sdk-ext-directories" ] + rebase_path(sdk_ext_directory)
+           [ "--sdk-ext-directories" ] + rebase_path(sdk_ext_directory) +
+           [ "--sdk-ext-files" ] + rebase_path(sdk_ext_files)
   }
 }