Markdown: always generate id attributes on headers

By generating id attributes even if [TOC] is not used, pages
can link to specific sections by header text.

Change-Id: I65939906d686120ac93b3087b1792e63def27c42

gitiles-servlet/src/main/java/com/google/gitiles/doc/MarkdownToHtml.java

diff --git a/gitiles-servlet/src/main/java/com/google/gitiles/doc/MarkdownToHtml.java b/gitiles-servlet/src/main/java/com/google/gitiles/doc/MarkdownToHtml.java
index 2721299..2ff8aeb 100644
--- a/gitiles-servlet/src/main/java/com/google/gitiles/doc/MarkdownToHtml.java
+++ b/gitiles-servlet/src/main/java/com/google/gitiles/doc/MarkdownToHtml.java
@@ -172,9 +172,7 @@
   public void visit(HeaderNode node) {
     String tag = "h" + node.getLevel();
     html.open(tag);
-    if (toc.include(node)) {
-      html.attribute("id", toc.idFromHeader(node));
-    }
+    html.attribute("id", toc.idFromHeader(node));
     visitChildren(node);
     html.close(tag);
   }