Add a method for rendering CSS templates.

The renderer needs to know what type of template it generates to return
correct types.

Google-Bug-Id: b/266904943
Release-Notes: skip
Change-Id: I0c0350d1d2254e0e24335e8ff2176c40519e32d6
diff --git a/java/com/google/gerrit/server/mail/send/OutgoingEmail.java b/java/com/google/gerrit/server/mail/send/OutgoingEmail.java
index 9f81b69..1eebf32 100644
--- a/java/com/google/gerrit/server/mail/send/OutgoingEmail.java
+++ b/java/com/google/gerrit/server/mail/send/OutgoingEmail.java
@@ -24,6 +24,7 @@
 import com.google.common.collect.Sets;
 import com.google.common.flogger.FluentLogger;
 import com.google.gerrit.common.Nullable;
+import com.google.gerrit.common.UsedAt;
 import com.google.gerrit.entities.Account;
 import com.google.gerrit.entities.Address;
 import com.google.gerrit.entities.EmailHeader;
@@ -790,6 +791,12 @@
     return configureRenderer(name).renderHtml().get();
   }
 
+  /** Renders a soy template of kind="css". */
+  @UsedAt(UsedAt.Project.GOOGLE)
+  public SanitizedContent soyCssTemplate(String name) {
+    return configureRenderer(name).renderCss().get();
+  }
+
   /** Configures a soy renderer for the given template name and rendering data map. */
   private SoySauce.Renderer configureRenderer(String templateName) {
     int baseNameIndex = templateName.indexOf("_");