Make the fuchsia mojo/public repo the source of truth.

mojo/public/platform/dart/BUILD.gn

Index: mojo/public/platform/dart/BUILD.gn
diff --git a/mojo/public/platform/dart/BUILD.gn b/mojo/public/platform/dart/BUILD.gn
deleted file mode 100644
index 7e3fd436b6b1ddefddedf04f66831e2321dea12f..0000000000000000000000000000000000000000
--- a/mojo/public/platform/dart/BUILD.gn
+++ /dev/null
@@ -1,24 +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_sdk.gni")
-
-mojo_sdk_source_set("mojo_internal_impl") {
-  sources = [
-    "dart_handle_watcher.cc",
-    "dart_handle_watcher.h",
-    "mojo_natives.cc",
-    "mojo_natives.h",
-  ]
-
-  deps = [
-    "//dart/runtime:libdart",
-  ]
-
-  mojo_sdk_public_deps = [
-    "mojo/public/c:system",
-    "mojo/public/cpp/environment",
-    "mojo/public/cpp/system",
-  ]
-}