SoyConstants: Make constants final

Change-Id: I8d9e89ebbc73870c98e1f9d9b5df4e5d19284657

java/com/google/gitiles/doc/SoyConstants.java

diff --git a/java/com/google/gitiles/doc/SoyConstants.java b/java/com/google/gitiles/doc/SoyConstants.java
index 48f1ede..042551f 100644
--- a/java/com/google/gitiles/doc/SoyConstants.java
+++ b/java/com/google/gitiles/doc/SoyConstants.java
@@ -33,7 +33,7 @@
    * <p>Based on {@link
    * com.google.template.soy.shared.internal.EscapingConventions.FilterImageDataUri}.
    */
-  static String IMAGE_URI_INNOCUOUS_OUTPUT = "data:image/gif;base64,zSoyz";
+  static final String IMAGE_URI_INNOCUOUS_OUTPUT = "data:image/gif;base64,zSoyz";
 
   /**
    * Innocuous output when a URI fails escaping.
@@ -46,7 +46,7 @@
    * <p>Based on {@link
    * com.google.template.soy.shared.internal.EscapingConventions.FilterNormalizeUri}.
    */
-  static String NORMAL_URI_INNOCUOUS_OUTPUT = "about:invalid#zSoyz";
+  static final String NORMAL_URI_INNOCUOUS_OUTPUT = "about:invalid#zSoyz";
 
   private SoyConstants() {}
 }