gn: Support build directories outside the source tree.

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 <vector>
 
 #include "base/basictypes.h"
 #include "base/strings/string_piece.h"
 #include "tools/gn/label_pattern.h"
 #include "tools/gn/source_dir.h"
 
 class Err;
 class Item;
 class Label;
 class Scope;
 class Value;
 
 class Visibility {
  public:
   // Defaults to private visibility (only the current file).
   Visibility();
   ~Visibility();
 
   // Set the visibility to the thing specified by the given value. On failure,
   // returns false and sets the error.
-  bool Set(const SourceDir& current_dir, const Value& value, Err* err);
+  bool Set(const base::FilePath& source_root,
+           const SourceDir& current_dir, const Value& value, Err* err);
 
   // Sets the visibility to be public.
   void SetPublic();
 
   // Sets the visibility to be private to the given directory.
   void SetPrivate(const SourceDir& current_dir);
 
   // Returns true if the target with the given label can depend on one with the
   // current visibility.
   bool CanSeeMe(const Label& label) const;
@@ skipping 12 matching lines @@
   // 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_