Revert "Remove unused WEB_BROWSER access path"

This reverts commit c3f9435aeb.
gerrit-review web session glue code currently uses this enum value.
Leave it in tree until sessions from plugins are better supported.

Change-Id: I6c246e3fb9861023b85ceaa4f42f72c3cc0dc864

gerrit-server/src/main/java/com/google/gerrit/server/AccessPath.java

@@ -25,6 +25,9 @@ public enum AccessPath {
   /** Access through the old JSON-RPC interface. */
   JSON_RPC,
 
+  /** Access by a web cookie. This path is not protected like REST_API. */
+  WEB_BROWSER,
+
   /** Access through an SSH command that is not invoked by Git. */
   SSH_COMMAND,