Load prettify.css for README.md files

If README.md is being rendered inline below a commit or a tree there
may be syntax highlighted code blocks.  Include prettify.css just in
case to ensure they render correctly.

Change-Id: I0b67b8912524a8d6fc1e2b95c4723ff3e5e1b09d
diff --git a/gitiles-servlet/src/main/resources/com/google/gitiles/templates/PathDetail.soy b/gitiles-servlet/src/main/resources/com/google/gitiles/templates/PathDetail.soy
index e42ee97..e2349d2 100644
--- a/gitiles-servlet/src/main/resources/com/google/gitiles/templates/PathDetail.soy
+++ b/gitiles-servlet/src/main/resources/com/google/gitiles/templates/PathDetail.soy
@@ -33,7 +33,7 @@
   {/call}
 {elseif $data.readmeHtml}
   {call .header data="all"}
-    {param css: [gitiles.DOC_CSS_URL] /}
+    {param css: [gitiles.DOC_CSS_URL, gitiles.PRETTIFY_CSS_URL] /}
   {/call}
 {else}
   {call .header data="all" /}
diff --git a/gitiles-servlet/src/main/resources/com/google/gitiles/templates/RevisionDetail.soy b/gitiles-servlet/src/main/resources/com/google/gitiles/templates/RevisionDetail.soy
index 3b2fcc2..cfed23e 100644
--- a/gitiles-servlet/src/main/resources/com/google/gitiles/templates/RevisionDetail.soy
+++ b/gitiles-servlet/src/main/resources/com/google/gitiles/templates/RevisionDetail.soy
@@ -36,7 +36,7 @@
   {/call}
 {elseif $hasReadme}
   {call .header data="all"}
-    {param css: [gitiles.DOC_CSS_URL] /}
+    {param css: [gitiles.DOC_CSS_URL, gitiles.PRETTIFY_CSS_URL] /}
   {/call}
 {else}
   {call .header data="all" /}