Windows precompiled header support in GN

tools/gn/path_output.h

Index: tools/gn/path_output.h
diff --git a/tools/gn/path_output.h b/tools/gn/path_output.h
index f7beb42357e3cd26d5a22df0fdab25dd5a8bd1b2..46c1aa96b2a80702052925b7dc99435c30c4c099 100644
--- a/tools/gn/path_output.h
+++ b/tools/gn/path_output.h
@@ -12,6 +12,7 @@
 #include "base/strings/string_piece.h"
 #include "tools/gn/escape.h"
 #include "tools/gn/source_dir.h"
+#include "tools/gn/unique_vector.h"
 
 class OutputFile;
 class SourceFile;
@@ -55,6 +56,8 @@ class PathOutput {
   // write an initial space before the first item.
   void WriteFiles(std::ostream& out,
                   const std::vector<OutputFile>& files) const;
+  void WriteFiles(std::ostream& out,
+                  const UniqueVector<OutputFile>& files) const;
 
   // This variant assumes the dir ends in a trailing slash or is empty.
   void WriteDir(std::ostream& out,