Teach dart_package to understand the packages/ subdirectory

third_party/dart-packages/matcher/BUILD.gn

Index: third_party/dart-packages/matcher/BUILD.gn
diff --git a/third_party/dart-packages/matcher/BUILD.gn b/third_party/dart-packages/matcher/BUILD.gn
deleted file mode 100644
index 7548acc3a8775b8afecfa242d45b2438fdb44c62..0000000000000000000000000000000000000000
--- a/third_party/dart-packages/matcher/BUILD.gn
+++ /dev/null
@@ -1,28 +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("matcher") {
-  sources = [
-    "matcher/matcher.dart",
-    "matcher/mirror_matchers.dart",
-    "matcher/src/core_matchers.dart",
-    "matcher/src/description.dart",
-    "matcher/src/error_matchers.dart",
-    "matcher/src/expect.dart",
-    "matcher/src/future_matchers.dart",
-    "matcher/src/interfaces.dart",
-    "matcher/src/iterable_matchers.dart",
-    "matcher/src/map_matchers.dart",
-    "matcher/src/numeric_matchers.dart",
-    "matcher/src/operator_matchers.dart",
-    "matcher/src/pretty_print.dart",
-    "matcher/src/prints_matcher.dart",
-    "matcher/src/string_matchers.dart",
-    "matcher/src/throws_matcher.dart",
-    "matcher/src/throws_matchers.dart",
-    "matcher/src/util.dart",
-  ]
-}