Bot update!

scripts/slave/chromium_commands.py

Index: scripts/slave/chromium_commands.py
diff --git a/scripts/slave/chromium_commands.py b/scripts/slave/chromium_commands.py
index 9c8b82e023311b74aac87c0e6558e0d6e898d511..c44efa82211d3bd005525f7d97a86878d79447bd 100644
--- a/scripts/slave/chromium_commands.py
+++ b/scripts/slave/chromium_commands.py
@@ -269,6 +269,7 @@ class GClient(SourceBaseCommand):
     self.no_gclient_revision = args.get('no_gclient_revision', False)
     self.gclient_transitive = args.get('gclient_transitive')
     self.gclient_jobs = args.get('gclient_jobs')
+    self.do_nothing = False
 
   def start(self):
     """Start the update process.
@@ -287,8 +288,21 @@ class GClient(SourceBaseCommand):
     self.sourcedatafile = os.path.join(self.builder.basedir,
                                        self.srcdir,
                                        ".buildbot-sourcedata")
+    self.do_nothing = os.path.isfile(os.path.join(self.builder.basedir,
+                                                  self.srcdir,
+                                                  'update.flag'))
+
+    d = defer.succeed(0)
+
+    if self.do_nothing:
+      # If bot update is run, we don't need to run the traditional update step.
+      msg = 'update.flag file found: bot_update has run and checkout is \n'
+      msg += 'already in a consistent state.\n'
+      msg += 'No actions will be performed in this step.'
+      self.sendStatus({'header': msg})
+      d.addCallback(self._sendRC)
+      return d
 
-    d = defer.succeed(None)
     # Do we need to clobber anything?
     if self.mode in ("copy", "clobber", "export"):
       d.addCallback(self.doClobber, self.workdir)