Markdown: fix inlined images from navbar.md

Soy requires wrapping the image data: URI inside of a SanitizedContent
after verifying it is well formed using a Sanitizer.

Change-Id: Ifb534230c9e8d9c661cd6b3e90b1c5a18ddbeb1b
diff --git a/gitiles-servlet/src/main/java/com/google/gitiles/doc/Navbar.java b/gitiles-servlet/src/main/java/com/google/gitiles/doc/Navbar.java
index cec14b8..3229b47 100644
--- a/gitiles-servlet/src/main/java/com/google/gitiles/doc/Navbar.java
+++ b/gitiles-servlet/src/main/java/com/google/gitiles/doc/Navbar.java
@@ -63,7 +63,7 @@
         } else if (HtmlBuilder.isImageDataUri(url)) {
           src = Sanitizers.filterImageDataUri(url);
         } else if (img != null) {
-          src = img.loadImage(url);
+          src = Sanitizers.filterImageDataUri(img.loadImage(url));
         } else {
           src = FilterImageDataUri.INSTANCE.getInnocuousOutput();
         }