gn format: penalty-based line breaking WIP XXX

tools/gn/parse_tree.h

Index: tools/gn/parse_tree.h
diff --git a/tools/gn/parse_tree.h b/tools/gn/parse_tree.h
index 60d15700c0189af8d63c97b0253e96308a59a003..573b1829b4c41f203394de7b396489104c67fb80 100644
--- a/tools/gn/parse_tree.h
+++ b/tools/gn/parse_tree.h
@@ -227,6 +227,7 @@ class BlockNode : public ParseNode {
   void Print(std::ostream& out, int indent) const override;
 
   void set_begin_token(const Token& t) { begin_token_ = t; }
+  const Token& begin_token() const { return begin_token_; }
   void set_end(scoped_ptr<EndNode> e) { end_ = e.Pass(); }
   const EndNode* End() const { return end_.get(); }
 
@@ -370,6 +371,7 @@ class ListNode : public ParseNode {
   void Print(std::ostream& out, int indent) const override;
 
   void set_begin_token(const Token& t) { begin_token_ = t; }
+  const Token& begin_token() const { return begin_token_; }
   void set_end(scoped_ptr<EndNode> e) { end_ = e.Pass(); }
   const EndNode* End() const { return end_.get(); }