Better performance on long lists containing comments.

lib/src/chunk_builder.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // 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.
 
 library dart_style.src.chunk_builder;
 
 import 'chunk.dart';
 import 'dart_formatter.dart';
 import 'debug.dart' as debug;
 import 'line_writer.dart';
@@ skipping 366 matching lines @@
   ///
   /// If [rule] is omitted, defaults to a new [Rule].
   void startLazyRule([Rule rule]) {
     if (rule == null) rule = new Rule();
 
     _lazyRules.add(rule);
   }
 
   /// Ends the innermost rule.
   void endRule() {
-    _rules.removeLast();
+    if (_lazyRules.isNotEmpty) {
+      _lazyRules.removeLast();
+    } else {
+      _rules.removeLast();
+    }
   }
 
   /// Pre-emptively forces all of the current rules to become hard splits.
   ///
   /// This is called by [SourceVisitor] when it can determine that a rule will
   /// will always be split. Turning it (and the surrounding rules) into hard
   /// splits lets the writer break the output into smaller pieces for the line
   /// splitter, which helps performance and avoids failing on very large input.
   ///
   /// In particular, it's easy for the visitor to know that collections with a
@@ skipping 404 matching lines @@
 
     // Discard spans in hardened chunks since we know for certain they will
     // split anyway.
     for (var chunk in _chunks) {
       if (chunk.rule != null && chunk.rule.isHardened) {
         chunk.spans.clear();
       }
     }
   }
 }