[GN]: Precompiled header support for GCC.

tools/gn/tool.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_TOOL_H_
 #define TOOLS_GN_TOOL_H_
 
 #include <string>
 
 #include "base/logging.h"
 #include "base/macros.h"
 #include "tools/gn/substitution_list.h"
 #include "tools/gn/substitution_pattern.h"
 
 class Tool {
  public:
   enum DepsFormat {
     DEPS_GCC = 0,
     DEPS_MSVC = 1
   };
 
   enum PrecompiledHeaderType {
     PCH_NONE = 0,
-    PCH_MSVC = 1
+    PCH_GCC = 1,
+    PCH_MSVC = 2
   };
 
   Tool();
   ~Tool();
 
   // Getters/setters ----------------------------------------------------------
   //
   // After the tool has had its attributes set, the caller must call
   // SetComplete(), at which point no other changes can be made.
 
@@ skipping 157 matching lines @@
   SubstitutionPattern rspfile_content_;
 
   bool complete_;
 
   SubstitutionBits substitution_bits_;
 
   DISALLOW_COPY_AND_ASSIGN(Tool);
 };
 
 #endif  // TOOLS_GN_TOOL_H_