validation_pool: Prep for pickling change.

Add an additional ValidationPool argument that is ignored for the sake
for an upcoming value that needs to be preserved during pickling.

BUG=chromium:549844
TEST=cbuildbot/run_tests --network

Change-Id: I0a4b1f1b96bb47f37b53ab92b7dc944fd0ac6630
Reviewed-on: https://chromium-review.googlesource.com/312116
Commit-Ready: Don Garrett <dgarrett@chromium.org>
Tested-by: Don Garrett <dgarrett@chromium.org>
Reviewed-by: David James <davidjames@chromium.org>
diff --git a/cbuildbot/validation_pool.py b/cbuildbot/validation_pool.py
index c5aa5e0..15f18e9 100644
--- a/cbuildbot/validation_pool.py
+++ b/cbuildbot/validation_pool.py
@@ -1122,7 +1122,7 @@
   def __init__(self, overlays, build_root, build_number, builder_name,
                is_master, dryrun, changes=None, non_os_changes=None,
                conflicting_changes=None, pre_cq_trybot=False,
-               tree_was_open=True, builder_run=None):
+               tree_was_open=True, _applied=None, builder_run=None):
     """Initializes an instance by setting default variables to instance vars.
 
     Generally use AcquirePool as an entry pool to a pool rather than this
@@ -1144,11 +1144,12 @@
       pre_cq_trybot: If set to True, this is a Pre-CQ trybot. (Note: The Pre-CQ
         launcher is NOT considered a Pre-CQ trybot.)
       tree_was_open: Whether the tree was open when the pool was created.
+      applied: List of CLs that have been applied to the current repo. Not
+        yet used, but needs to be here for pickling compatibility.
       builder_run: BuilderRun instance used to fetch cidb handle and metadata
         instance. Please note due to the pickling logic, this MUST be the last
         kwarg listed.
     """
-
     self.build_root = build_root
 
     # These instances can be instantiated via both older, or newer pickle