Enhance GN diagnostic tools

tools/gn/pattern.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_PATTERN_H_
 #define TOOLS_GN_PATTERN_H_
 
 #include <string>
 #include <vector>
 
 #include "tools/gn/value.h"
 
-extern const char kPattern_Help[];
-
 class Pattern {
  public:
   struct Subrange {
     enum Type {
       LITERAL,  // Matches exactly the contents of the string.
       ANYTHING,  // * (zero or more chars).
       PATH_BOUNDARY  // '/' or beginning of string.
     };
 
     Subrange(Type t, const std::string& l = std::string())
@@ skipping 56 matching lines @@
   void SetFromValue(const Value& v, Err* err);
 
   bool MatchesString(const std::string& s) const;
   bool MatchesValue(const Value& v) const;
 
  private:
   std::vector<Pattern> patterns_;
 };
 
 #endif  // TOOLS_GN_PATTERN_H_