Update dart:mirrors to use Symbol.

dart/runtime/lib/collection_dev_sources.gypi

Index: dart/runtime/lib/collection_dev_sources.gypi
diff --git a/dart/runtime/lib/mirrors_sources.gypi b/dart/runtime/lib/collection_dev_sources.gypi
similarity index 55%
copy from dart/runtime/lib/mirrors_sources.gypi
copy to dart/runtime/lib/collection_dev_sources.gypi
index a0528474d0a7343b3ce5047cffc3314df8ddabca..76121f5426e529898584e2030321bca8c4e1fba8 100644
--- a/dart/runtime/lib/mirrors_sources.gypi
+++ b/dart/runtime/lib/collection_dev_sources.gypi
@@ -2,13 +2,12 @@
 # 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.
 
-# Implementation sources.
+# Sources that patch the library "dart:_collection-dev".
 
 {
   'sources': [
-    'mirrors.cc',
-    'mirrors.h',
-    'mirrors_patch.dart',
-    'mirrors_impl.dart',
+    'collection_dev_patch.dart',
+    # The above file needs to be first as it imports required libraries.
+    'symbol_patch.dart',
   ],
 }