gn: Support build directories outside the source tree.

tools/gn/label_pattern.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_LABEL_PATTERN_H_
 #define TOOLS_GN_LABEL_PATTERN_H_
 
 #include "base/strings/string_piece.h"
 #include "tools/gn/label.h"
 #include "tools/gn/source_dir.h"
@@ skipping 17 matching lines @@
 
   LabelPattern();
   LabelPattern(Type type,
                const SourceDir& dir,
                const base::StringPiece& name,
                const Label& toolchain_label);
   ~LabelPattern();
 
   // Converts the given input string to a pattern. This does special stuff
   // to treat the pattern as a label. Sets the error on failure.
-  static LabelPattern GetPattern(const SourceDir& current_dir,
+  static LabelPattern GetPattern(const base::FilePath& source_root,
+                                 const SourceDir& current_dir,
                                  const Value& value,
                                  Err* err);
 
   // Returns true if this pattern matches the given label.
   bool Matches(const Label& label) const;
 
   // Returns a string representation of this pattern.
   std::string Describe() const;
 
   Type type() const { return type_; }
@@ skipping 14 matching lines @@
   // Used when type_ == PRIVATE and PRIVATE_RECURSIVE. This specifies the
   // directory that to which the pattern is private to.
   SourceDir dir_;
 
   // Empty name means match everything. Otherwise the name must match
   // exactly.
   std::string name_;
 };
 
 #endif  // TOOLS_GN_LABEL_PATTERN_H_