Cache user roles during WorkRequestContext lifetime

This speeds up building the tool module by a factor of 5.

lib/galaxy/work/context.py

@@ -22,6 +22,7 @@ class WorkRequestContext(ProvidesAppContext, ProvidesUserContext, ProvidesHistor
         self.app = app
         self.security = app.security
         self.__user = user
+        self.__user_current_roles = None
         self.__history = history
         self.api_inherit_admin = False
         self.workflow_building_mode = workflow_building_mode
@@ -40,6 +41,12 @@ class WorkRequestContext(ProvidesAppContext, ProvidesUserContext, ProvidesHistor
         """Return the current user if logged in or None."""
         return self.__user
 
+    def get_current_user_roles(self):
+        if not self.__user_current_roles:
+            if self.__user:
+                self.__user_current_roles = self.__user.all_roles()
+        return self.__user_current_roles
+
     def set_user(self, user):
         """Set the current user."""
         raise NotImplementedError("Cannot change users from a work request context.")