[infra] Translate _sources.gypi files to _sources.gni files

sdk/lib/internal/internal_sources.gni

Index: sdk/lib/internal/internal_sources.gni
diff --git a/sdk/lib/internal/internal_sources.gni b/sdk/lib/internal/internal_sources.gni
new file mode 100644
index 0000000000000000000000000000000000000000..9f7db6b509bcf28084c4681a35a9d578d5dba07a
--- /dev/null
+++ b/sdk/lib/internal/internal_sources.gni
@@ -0,0 +1,16 @@
+# Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+# for details. All rights reserved. Use of this source code is governed by a
+# BSD-style license that can be found in the LICENSE file.
+
+# This file contains all sources for the dart:_internal library.
+internal_sdk_sources = [
+  "internal.dart",
+
+  # The above file needs to be first as it lists the parts below.
+  "iterable.dart",
+  "list.dart",
+  "linked_list.dart",
+  "print.dart",
+  "sort.dart",
+  "symbol.dart",
+]