Add missing final for MarkdownConfig.CONFIG_PARSER

Change-Id: Ifb6b9ff19643e843f65848523806af15fc50d7f0
diff --git a/gitiles-servlet/src/main/java/com/google/gitiles/doc/MarkdownConfig.java b/gitiles-servlet/src/main/java/com/google/gitiles/doc/MarkdownConfig.java
index 79ddbb6..1982e5a 100644
--- a/gitiles-servlet/src/main/java/com/google/gitiles/doc/MarkdownConfig.java
+++ b/gitiles-servlet/src/main/java/com/google/gitiles/doc/MarkdownConfig.java
@@ -27,7 +27,7 @@
     return cfg.get(CONFIG_PARSER);
   }
 
-  private static SectionParser<MarkdownConfig> CONFIG_PARSER =
+  private static final SectionParser<MarkdownConfig> CONFIG_PARSER =
       new SectionParser<MarkdownConfig>() {
         @Override
         public MarkdownConfig parse(Config cfg) {