Invoke roll-dep with a git hash.

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 48 matching lines @@
     self.GitCreateBranch("v8-roll-%s" % self["trunk_revision"],
                          cwd=self._options.chromium)
 
 
 class UploadCL(Step):
   MESSAGE = "Create and upload CL."
 
   def RunStep(self):
     # Patch DEPS file.
     if self.Command(
-        "roll-dep", "v8 %s" % self["trunk_revision"],
+        "roll-dep", "v8 %s" % self["last_push"],
         cwd=self._options.chromium) 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),
@@ skipping 67 matching lines @@
       SwitchChromium,
       UpdateChromiumCheckout,
       UploadCL,
       SwitchV8,
       CleanUp,
     ]
 
 
 if __name__ == "__main__":  # pragma: no cover
   sys.exit(ChromiumRoll().Run())