Adjust master_gen.PopulateBuildmasterConfig() to look at master_site_config

masters/master.chromium.mojo/master.cfg

Index: masters/master.chromium.mojo/master.cfg
diff --git a/masters/master.chromium.mojo/master.cfg b/masters/master.chromium.mojo/master.cfg
index 222fd4c7aae515625844d16cc91451642ebb74c9..4ec3a641f158ffa1efd800584bbd1a79ce96dfea 100644
--- a/masters/master.chromium.mojo/master.cfg
+++ b/masters/master.chromium.mojo/master.cfg
@@ -10,6 +10,8 @@
 
 import os
 
+import master_site_config
+
 # This module comes from scripts/, which must be in the PYTHONPATH.
 from master import master_gen
 
@@ -20,4 +22,5 @@ BuildmasterConfig = {}
 
 master_gen.PopulateBuildmasterConfig(
     BuildmasterConfig,
-    os.path.join(os.path.dirname(os.path.abspath(__file__)), 'builders.pyl'))
+    os.path.join(os.path.dirname(os.path.abspath(__file__)), 'builders.pyl'),
+    master_site_config.ChromiumMojo)