Teach dart_package to understand the packages/ subdirectory

third_party/dart-packages/crypto/BUILD.gn

Index: third_party/dart-packages/crypto/BUILD.gn
diff --git a/third_party/dart-packages/crypto/BUILD.gn b/third_party/dart-packages/crypto/BUILD.gn
deleted file mode 100644
index 7dcbeded847a492b6989cac8197624df6fb26306..0000000000000000000000000000000000000000
--- a/third_party/dart-packages/crypto/BUILD.gn
+++ /dev/null
@@ -1,17 +0,0 @@
-# Copyright 2015 The Chromium Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
-
-import("//mojo/public/dart/rules.gni")
-
-dart_package("crypto") {
-  sources = [
-    "crypto/crypto.dart",
-    "crypto/src/crypto_utils.dart",
-    "crypto/src/hash_utils.dart",
-    "crypto/src/hmac.dart",
-    "crypto/src/md5.dart",
-    "crypto/src/sha1.dart",
-    "crypto/src/sha256.dart",
-  ]
-}