gn format: penalty-based scheme for line breaking

tools/gn/parse_tree.cc

 // Copyright (c) 2013 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.
 
 #include "tools/gn/parse_tree.h"
 
 #include <string>
 
 #include "base/stl_util.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 420 matching lines @@
   return Err(value_, msg, help);
 }
 
 void IdentifierNode::Print(std::ostream& out, int indent) const {
   out << IndentFor(indent) << "IDENTIFIER(" << value_.value() << ")\n";
   PrintComments(out, indent);
 }
 
 // ListNode -------------------------------------------------------------------
 
-ListNode::ListNode() {
+ListNode::ListNode() : prefer_multiline_(false) {
 }
 
 ListNode::~ListNode() {
   STLDeleteContainerPointers(contents_.begin(), contents_.end());
 }
 
 const ListNode* ListNode::AsList() const {
   return this;
 }
 
@@ skipping 22 matching lines @@
   return LocationRange(begin_token_.location(),
                        end_->value().location());
 }
 
 Err ListNode::MakeErrorDescribing(const std::string& msg,
                                   const std::string& help) const {
   return Err(begin_token_, msg, help);
 }
 
 void ListNode::Print(std::ostream& out, int indent) const {
-  out << IndentFor(indent) << "LIST\n";
+  out << IndentFor(indent) << "LIST" << (prefer_multiline_ ? " multiline" : "")
+      << "\n";
   PrintComments(out, indent);
   for (const auto& cur : contents_)
     cur->Print(out, indent + 1);
   if (end_ && end_->comments())
     end_->Print(out, indent + 1);
 }
 
 // LiteralNode -----------------------------------------------------------------
 
 LiteralNode::LiteralNode() {
@@ skipping 135 matching lines @@
 
 Err EndNode::MakeErrorDescribing(const std::string& msg,
                                         const std::string& help) const {
   return Err(value_, msg, help);
 }
 
 void EndNode::Print(std::ostream& out, int indent) const {
   out << IndentFor(indent) << "END(" << value_.value() << ")\n";
   PrintComments(out, indent);
 }