Add a "gn path" command for finding deps.

tools/gn/commands.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_COMMANDS_H_
 #define TOOLS_GN_COMMANDS_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 50 matching lines @@
 extern const char kHelp[];
 extern const char kHelp_HelpShort[];
 extern const char kHelp_Help[];
 int RunHelp(const std::vector<std::string>& args);
 
 extern const char kLs[];
 extern const char kLs_HelpShort[];
 extern const char kLs_Help[];
 int RunLs(const std::vector<std::string>& args);
 
+extern const char kPath[];
+extern const char kPath_HelpShort[];
+extern const char kPath_Help[];
+int RunPath(const std::vector<std::string>& args);
+
 extern const char kRefs[];
 extern const char kRefs_HelpShort[];
 extern const char kRefs_Help[];
 int RunRefs(const std::vector<std::string>& args);
 
 // -----------------------------------------------------------------------------
 
 struct CommandInfo {
   CommandInfo();
   CommandInfo(const char* in_help_short,
@@ skipping 86 matching lines @@
 // If indent is true, the results will be indented two spaces.
 //
 // The vector will be modified so that only the printed targets will remain.
 void FilterAndPrintTargets(bool indent, std::vector<const Target*>* targets);
 void FilterAndPrintTargetSet(bool indent,
                              const std::set<const Target*>& targets);
 
 }  // namespace commands
 
 #endif  // TOOLS_GN_COMMANDS_H_