Add dry-run feature to auto roll scripts.

tools/push-to-trunk/chromium_roll.py

 #!/usr/bin/env python
 # Copyright 2014 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import argparse
 import os
 import sys
 
 from common_includes import *
@@ skipping 69 matching lines @@
         "roll-dep", "v8 %s" % self["trunk_revision"]) is None:
       self.Die("Failed to create deps for %s" % self["trunk_revision"])
 
     commit_title = "Update V8 to %s." % self["push_title"].lower()
     sheriff = ""
     if self["sheriff"]:
       sheriff = ("\n\nPlease reply to the V8 sheriff %s in case of problems."
                  % self["sheriff"])
     self.GitCommit("%s%s\n\nTBR=%s" %
                    (commit_title, sheriff, self._options.reviewer))
-    self.GitUpload(author=self._options.author,
-                   force=True,
-                   cq=self._options.use_commit_queue)
-    print "CL uploaded."
+    if not self._options.dry_run:
+      self.GitUpload(author=self._options.author,
+                     force=True,
+                     cq=self._options.use_commit_queue)
+      print "CL uploaded."
+    else:
+      self.GitCheckout("master")
+      self.GitDeleteBranch("v8-roll-%s" % self["trunk_revision"])
+      print "Dry run - don't upload."
 
 
 class SwitchV8(Step):
   MESSAGE = "Returning to V8 checkout."
 
   def RunStep(self):
     os.chdir(self["v8_path"])
 
 
 class CleanUp(Step):
@@ skipping 37 matching lines @@
       SwitchChromium,
       UpdateChromiumCheckout,
       UploadCL,
       SwitchV8,
       CleanUp,
     ]
 
 
 if __name__ == "__main__":  # pragma: no cover
   sys.exit(ChromiumRoll(CONFIG).Run())