Reset to correct version when switching upstream repository for a git dependency.

This avoids build errors like at http://build.chromium.org/p/tryserver.chromium/builders/linux_clang/builds/64851/steps/update/logs/stdio (search for mtpd).

BUG=none


Review URL: https://chromiumcodereview.appspot.com/11417059

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@168521 0039d316-1c4b-4281-b951-d872f2087c98

gclient_scm.py

@@ -314,7 +314,7 @@ class GitWrapper(SCMWrapper):
       if not options.verbose:
         quiet = ['--quiet']
       self._Run(['fetch', 'origin', '--prune'] + quiet, options)
-      self._Run(['reset', '--hard', 'origin/master'] + quiet, options)
+      self._Run(['reset', '--hard', revision] + quiet, options)
       self.UpdateSubmoduleConfig()
       files = self._Capture(['ls-files']).splitlines()
       file_list.extend([os.path.join(self.checkout_path, f) for f in files])