Set changeHorizon to put an upper-bound on database size, otherwise the database will never stop gr…

scripts/common/chromium_utils.py

Index: scripts/common/chromium_utils.py
diff --git a/scripts/common/chromium_utils.py b/scripts/common/chromium_utils.py
index 89bee7a154060c32dca5725109bb8ff01f004618..b4d30834c6b8853aa6b26d078d71ea4f39e540dd 100644
--- a/scripts/common/chromium_utils.py
+++ b/scripts/common/chromium_utils.py
@@ -1899,7 +1899,14 @@ def FileExclusions():
 
 
 def DatabaseSetup(buildmaster_config, require_dbconfig=False):
-  """Read database credentials in the master directory."""
+  """Configure the database settings for the buildbot master."""
+
+  # By default nothing is ever deleted from the database.  We set a
+  # changeHorizon here to put an upper bound on the database size.
+  if 'changeHorizon' not in buildmaster_config:
+    buildmaster_config['changeHorizon'] = 3000
+
+  # Read database credentials in the master directory.
   if os.path.isfile('.dbconfig'):
     values = {}
     execfile('.dbconfig', values)