Make DefaultUrls public

Other implementations may want to delegate their own GitilesUrls
implementations to this class, which is about as simple as can be.

Change-Id: I934b073851587f582b7f9177fd6c6d458201ef3c

gitiles-servlet/src/main/java/com/google/gitiles/DefaultUrls.java

diff --git a/gitiles-servlet/src/main/java/com/google/gitiles/DefaultUrls.java b/gitiles-servlet/src/main/java/com/google/gitiles/DefaultUrls.java
index 83c5436..7218a4b 100644
--- a/gitiles-servlet/src/main/java/com/google/gitiles/DefaultUrls.java
+++ b/gitiles-servlet/src/main/java/com/google/gitiles/DefaultUrls.java
@@ -27,12 +27,12 @@
  * This implementation uses statically-configured defaults, and thus assumes
  * that the servlet is running a single virtual host.
  */
-class DefaultUrls implements GitilesUrls {
+public class DefaultUrls implements GitilesUrls {
   private final String canonicalHostName;
   private final String baseGitUrl;
   private final String baseGerritUrl;
 
-  DefaultUrls(String canonicalHostName, String baseGitUrl, String baseGerritUrl)
+  public DefaultUrls(String canonicalHostName, String baseGitUrl, String baseGerritUrl)
       throws UnknownHostException {
     if (canonicalHostName != null) {
       this.canonicalHostName = canonicalHostName;