tools/gn: Add out-of-line copy ctors for complex classes.

tools/gn/label.h

 // Copyright (c) 2013 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_H_
 #define TOOLS_GN_LABEL_H_
 
 #include <stddef.h>
 
 #include "base/containers/hash_tables.h"
@@ skipping 11 matching lines @@
 
   // Makes a label given an already-separated out path and name.
   // See also Resolve().
   Label(const SourceDir& dir,
         const base::StringPiece& name,
         const SourceDir& toolchain_dir,
         const base::StringPiece& toolchain_name);
 
   // Makes a label with an empty toolchain.
   Label(const SourceDir& dir, const base::StringPiece& name);
+  Label(const Label& other);

[tfarina, 2016/02/24 19:13:48]

add empty lines before and after like in Err?

   ~Label();
 
   // Resolives a string from a build file that may be relative to the
   // current directory into a fully qualified label. On failure returns an
   // is_null() label and sets the error.
   static Label Resolve(const SourceDir& current_dir,
                        const Label& current_toolchain,
                        const Value& input,
                        Err* err);
 
@@ skipping 74 matching lines @@
   }
 };
 
 }  // namespace BASE_HASH_NAMESPACE
 
 inline void swap(Label& lhs, Label& rhs) {
   lhs.swap(rhs);
 }
 
 #endif  // TOOLS_GN_LABEL_H_