gn format: Have format sort sources

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 dcf678babc2966307453742a3a9567b20c3b5a87..4dd0485c5b18f61ffa8ee151bee87c7c1e797603 100644
--- a/tools/gn/parse_tree.h
+++ b/tools/gn/parse_tree.h
@@ -32,23 +32,18 @@ class Comments {
   virtual ~Comments();
 
   const std::vector<Token>& before() const { return before_; }
-  void append_before(Token c) {
-    before_.push_back(c);
-  }
+  void append_before(Token c) { before_.push_back(c); }
+  void clear_before() { before_.clear(); }
 
   const std::vector<Token>& suffix() const { return suffix_; }
-  void append_suffix(Token c) {
-    suffix_.push_back(c);
-  }
+  void append_suffix(Token c) { suffix_.push_back(c); }
   // Reverse the order of the suffix comments. When walking the tree in
   // post-order we append suffix comments in reverse order, so this fixes them
   // up.
   void ReverseSuffix();
 
   const std::vector<Token>& after() const { return after_; }
-  void append_after(Token c) {
-    after_.push_back(c);
-  }
+  void append_after(Token c) { after_.push_back(c); }
 
  private:
   // Whole line comments before the expression.
@@ -160,6 +155,8 @@ class AccessorNode : public ParseNode {
   const IdentifierNode* member() const { return member_.get(); }
   void set_member(scoped_ptr<IdentifierNode> i) { member_ = i.Pass(); }
 
+  void SetNewLocation(int line_number);
+
  private:
   Value ExecuteArrayAccess(Scope* scope, Err* err) const;
   Value ExecuteScopeAccess(Scope* scope, Err* err) const;
@@ -348,6 +345,8 @@ class IdentifierNode : public ParseNode {
   const Token& value() const { return value_; }
   void set_value(const Token& t) { value_ = t; }
 
+  void SetNewLocation(int line_number);
+
  private:
   Token value_;
 
@@ -378,6 +377,8 @@ class ListNode : public ParseNode {
   }
   const std::vector<const ParseNode*>& contents() const { return contents_; }
 
+  void SortAsStringsList();
+
   // During formatting, do we want this list to always be multliline? This is
   // used to make assignments to deps, sources, etc. always be multiline lists,
   // rather than collapsed to a single line when they're one element.
@@ -418,6 +419,8 @@ class LiteralNode : public ParseNode {
   const Token& value() const { return value_; }
   void set_value(const Token& t) { value_ = t; }
 
+  void SetNewLocation(int line_number);
+
  private:
   Token value_;