Add error handling when initializing the file system watcher

runtime/bin/file_patch.dart

Index: runtime/bin/file_patch.dart
diff --git a/runtime/bin/file_patch.dart b/runtime/bin/file_patch.dart
index 36e5b57e80d00cad20b6eb157b5200fe4eb592cc..14499af5182ed9afa940d6d1f35bef278f75870e 100644
--- a/runtime/bin/file_patch.dart
+++ b/runtime/bin/file_patch.dart
@@ -99,7 +99,7 @@ patch class _FileSystemWatcher {
         _newWatcher();
       } catch (e) {
         _broadcastController.addError(new FileSystemException(
-            "Failed to initialize file system entity watcher"));
+            "Failed to initialize file system entity watcher", null, e));
         _broadcastController.close();
         return;
       }