HelloWebLink: Make the dummy image more visible

Change-Id: If2b80d5fd2f719ebd1db4c9b15f5c8e50f5cda3f

src/main/java/com/googlesource/gerrit/plugins/cookbook/HelloWeblink.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/cookbook/HelloWeblink.java b/src/main/java/com/googlesource/gerrit/plugins/cookbook/HelloWeblink.java
index 48829c5..14200d9 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/cookbook/HelloWeblink.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/cookbook/HelloWeblink.java
@@ -31,7 +31,8 @@
       placeHolderUrlProject + "/commit=%s";
   private String placeHolderUrlProjectRevisionFileName =
       placeHolderUrlProject + "-revision=%s-file=%s";
-  private String myImageUrl = "http://placehold.it/16x16.gif";
+  private String myImageUrl =
+      "http://dummyimage.com/16x16/000000/ffffff.png&text=CB";
 
   @Override
   public WebLinkInfo getBranchWebLink(String projectName, String branchName) {