Gn: Add support to generate Visual Studio 2017 solutions.

tools/gn/visual_studio_writer.h

 // Copyright 2016 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_VISUAL_STUDIO_WRITER_H_
 #define TOOLS_GN_VISUAL_STUDIO_WRITER_H_
 
 #include <iosfwd>
 #include <memory>
 #include <string>
@@ skipping 10 matching lines @@
 class Builder;
 class BuildSettings;
 class Err;
 class SourceFile;
 class Target;
 
 class VisualStudioWriter {
  public:
   enum Version {
     Vs2013 = 1,  // Visual Studio 2013
-    Vs2015       // Visual Studio 2015
+    Vs2015,      // Visual Studio 2015
+    Vs2017       // Visual Studio 2017
   };
 
   // Writes Visual Studio project and solution files. |sln_name| is the optional
   // solution file name ("all" is used if not specified). |filters| is optional
   // semicolon-separated list of label patterns used to limit the set of
   // generated projects. Only matching targets and their dependencies (unless
   // |no_deps| is true) will be included to the solution. On failure will
   // populate |err| and will return false.
   static bool RunAndWriteFiles(const BuildSettings* build_settings,
                                const Builder& builder,
@@ skipping 104 matching lines @@
   // Semicolon-separated Windows SDK include directories.
   std::string windows_kits_include_dirs_;
 
   // Path formatter for ninja targets.
   PathOutput ninja_path_output_;
 
   DISALLOW_COPY_AND_ASSIGN(VisualStudioWriter);
 };
 
 #endif  // TOOLS_GN_VISUAL_STUDIO_WRITER_H_