Add font substituted metrics for OS other than Linux

pdf/out_of_process_instance.h

Index: pdf/out_of_process_instance.h
diff --git a/pdf/out_of_process_instance.h b/pdf/out_of_process_instance.h
index e2c0eacfde32047075967512fa26b1ca9d860d0a..755e653bd188a956b07280124bf96aeb520735ab 100644
--- a/pdf/out_of_process_instance.h
+++ b/pdf/out_of_process_instance.h
@@ -311,11 +311,9 @@ class OutOfProcessInstance : public pp::Instance,
   // the stats if a feature shows up many times per document.
   std::set<std::string> unsupported_features_reported_;
 
-#if defined(OS_LINUX)
   // Keeps track of whether font substitution has been reported, so we avoid
   // spamming the stats if a document requested multiple substitutes.
   bool font_substitution_reported_;
-#endif
 
   // Number of pages in print preview mode, 0 if not in print preview mode.
   int print_preview_page_count_;