Bump analyzer to 0.27.4.

lib/src/dart_formatter.dart

Index: lib/src/dart_formatter.dart
diff --git a/lib/src/dart_formatter.dart b/lib/src/dart_formatter.dart
index 4f5af4e8c4d914dd6ad613fc8ab5a88a0b2ed88f..73df998e2a7df9e1e472a88e9a2c17a93534e1ab 100644
--- a/lib/src/dart_formatter.dart
+++ b/lib/src/dart_formatter.dart
@@ -103,8 +103,6 @@ class DartFormatter {
     // Parse it.
     var parser = new Parser(stringSource, errorListener);
 
-    parser.parseTrailingCommas = true;
-
     var node;
     if (source.isCompilationUnit) {
       node = parser.parseCompilationUnit(startToken);