Add support for repeated keys in TaskRequest.

appengine/swarming/server/task_scheduler.py

Index: appengine/swarming/server/task_scheduler.py
diff --git a/appengine/swarming/server/task_scheduler.py b/appengine/swarming/server/task_scheduler.py
index 58714dfa3bdfd36f7fb2ec5cbbaa171ba04886dc..d6c640389817a52a6b7ba58f808542703f2066f6 100644
--- a/appengine/swarming/server/task_scheduler.py
+++ b/appengine/swarming/server/task_scheduler.py
@@ -350,19 +350,20 @@ def _check_dimension_acls(request):
 
   ident = request.authenticated
   dims = request.properties.dimensions
-  assert 'id' in dims or 'pool' in dims, dims # see _validate_dimensions
   assert ident is not None # see task_request.init_new_request
 
+  using_id = any(k == u'id' for k, _ in dims)
+  using_pool = any(k == u'pool' for k, _ in dims)
   # Forbid targeting individual bots for non-admins, but allow using 'id' if
   # 'pool' is used as well (so whoever can posts tasks to 'pool', can target an
   # individual bot in that pool).
-  if 'id' in dims and 'pool' not in dims:
+  if using_id and not using_pool:
     if not acl.is_admin():
       raise auth.AuthorizationError(
           'Only Swarming administrators can post tasks with "id" dimension '
           'without specifying a "pool" dimension.')
 
-  for k, v in sorted(dims.iteritems()):
+  for k, v in dims:
     if not _can_use_dimension(dim_acls, ident, k, v):
       raise auth.AuthorizationError(
           'User %s is not allowed to schedule tasks with dimension "%s:%s"' %