Resize the diffy avatar to be 26x26

Avatar images are expected to be square 26x26 boxes when used in
small comment regions. Resize the stock image used to identify the
Gerrit server to be 26x26, centering the diffy logo in the middle
of the region.

Bug: issue 2051
Change-Id: Iddf93d0da8b64cddcd34f8d772fdf50e754c78a6

gerrit-gwtui/src/main/java/com/google/gerrit/client/AvatarImage.java

@@ -71,7 +71,7 @@ public class AvatarImage extends Image implements LoadHandler {
       setVisible(false);
     } else if (isGerritServer(account)) {
       setVisible(true);
-      setResource(Gerrit.RESOURCES.gerritAvatar());
+      setResource(Gerrit.RESOURCES.gerritAvatar26());
     } else if (account.has_avatar_info()) {
       setVisible(false);
       AvatarInfo info = account.avatar(size);

gerrit-gwtui/src/main/java/com/google/gerrit/client/GerritResources.java

@@ -52,8 +52,8 @@ public interface GerritResources extends ClientBundle {
   @Source("addFileComment.png")
   public ImageResource addFileComment();
 
-  @Source("diffy.png")
+  @Source("diffy26.png")
-  public ImageResource gerritAvatar();
+  public ImageResource gerritAvatar26();
 
   @Source("draftComments.png")
   public ImageResource draftComments();