[GN] Add JSON project writer

tools/gn/visibility.h

 // Copyright 2014 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.
 
 #ifndef TOOLS_GN_VISIBILITY_H_
 #define TOOLS_GN_VISIBILITY_H_
 
+#include <memory>
 #include <vector>
 
 #include "base/macros.h"
 #include "tools/gn/label_pattern.h"
 #include "tools/gn/source_dir.h"
 
+namespace base {
+class Value;
+}
+
 class Err;
 class Item;
 class Label;
 class Scope;
 class Value;
 
 class Visibility {
  public:
   // Defaults to private visibility (only the current file).
   Visibility();
@@ skipping 12 matching lines @@
   // Returns true if the target with the given label can depend on one with the
   // current visibility.
   bool CanSeeMe(const Label& label) const;
 
   // Returns a string listing the visibility. |indent| number of spaces will
   // be added on the left side of the output. If |include_brackets| is set, the
   // result will be wrapped in "[ ]" and the contents further indented. The
   // result will end in a newline.
   std::string Describe(int indent, bool include_brackets) const;
 
+  // Returns value representation of this visibility
+  std::unique_ptr<base::Value> AsValue() const;
+
   // Helper function to check visibility between the given two items. If
   // to is invisible to from, returns false and sets the error.
   static bool CheckItemVisibility(const Item* from, const Item* to, Err* err);
 
   // Helper function to fill an item's visibility from the "visibility" value
   // in the current scope.
   static bool FillItemVisibility(Item* item, Scope* scope, Err* err);
 
  private:
   std::vector<LabelPattern> patterns_;
 
   DISALLOW_COPY_AND_ASSIGN(Visibility);
 };
 
 #endif  // TOOLS_GN_VISIBILITY_H_