gn: start of format command

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 e3d4e7d7f93fb343c65ecea7c631f96451d065a6..2ddd095df2799d80b4acb6eb1589321e05446324 100644
--- a/tools/gn/parse_tree.h
+++ b/tools/gn/parse_tree.h
@@ -24,6 +24,7 @@ class ListNode;
 class LiteralNode;
 class Scope;
 class UnaryOpNode;
+class BlockCommentNode;
 
 class Comments {
  public:
@@ -80,6 +81,7 @@ class ParseNode {
   virtual const ListNode* AsList() const;
   virtual const LiteralNode* AsLiteral() const;
   virtual const UnaryOpNode* AsUnaryOp() const;
+  virtual const BlockCommentNode* AsBlockComment() const;
 
   virtual Value Execute(Scope* scope, Err* err) const = 0;
 
@@ -438,4 +440,33 @@ class UnaryOpNode : public ParseNode {
   DISALLOW_COPY_AND_ASSIGN(UnaryOpNode);
 };
 
+// BlockCommentNode ------------------------------------------------------------
+
+// This node type is only used for standalone comments (that is, those not
+// specifically attached to another syntax element. The most common of these
+// is a copyright header block. This node contains only the last line of such
+// a comment block as the anchor, and other lines of the block comment are
+// hung off of it as Before comments, similar to other syntax elements.
+class BlockCommentNode : public ParseNode {
+ public:
+  BlockCommentNode();
+  virtual ~BlockCommentNode();
+
+  virtual const BlockCommentNode* AsBlockComment() const OVERRIDE;
+  virtual Value Execute(Scope* scope, Err* err) const OVERRIDE;
+  virtual LocationRange GetRange() const OVERRIDE;
+  virtual Err MakeErrorDescribing(
+      const std::string& msg,
+      const std::string& help = std::string()) const OVERRIDE;
+  virtual void Print(std::ostream& out, int indent) const OVERRIDE;
+
+  const Token& comment() const { return comment_; }
+  void set_comment(const Token& t) { comment_ = t; }
+
+ private:
+  Token comment_;
+
+  DISALLOW_COPY_AND_ASSIGN(BlockCommentNode);
+};
+
 #endif  // TOOLS_GN_PARSE_TREE_H_