Don't let roll scripts use short hashes

tools/roll_webgl_conformance.py

 #!/usr/bin/env python
 # Copyright 2015 The Chromium 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 collections
 import logging
 import os
 import re
@@ skipping 146 matching lines @@
     if not ignore_exit_code and p.returncode != 0:
       logging.error('Command failed: %s\n%s', str(command), output)
       sys.exit(p.returncode)
     return output
 
   def _GetCommitInfo(self, path_below_src, git_hash=None, git_repo_url=None):
     working_dir = os.path.join(self._chromium_src, path_below_src)
     self._RunCommand(['git', 'fetch', 'origin'], working_dir=working_dir)
     revision_range = git_hash or 'origin'
     ret = self._RunCommand(
-        ['git', '--no-pager', 'log', revision_range, '--pretty=full', '-1'],
+        ['git', '--no-pager', 'log', revision_range,
+         '--no-abbrev-commit', '--pretty=full', '-1'],
         working_dir=working_dir)
     return CommitInfo(_ParseGitCommitHash(ret), git_repo_url)
 
   def _GetDepsCommitInfo(self, deps_dict, path_below_src):
     entry = deps_dict['deps'][_PosixPath('src/%s' % path_below_src)]
     at_index = entry.find('@')
     git_repo_url = entry[:at_index]
     git_hash = entry[at_index + 1:]
     return self._GetCommitInfo(path_below_src, git_hash, git_repo_url)
 
@@ skipping 209 matching lines @@
     logging.basicConfig(level=logging.ERROR)
 
   autoroller = AutoRoller(SRC_DIR)
   if args.abort:
     return autoroller.Abort()
   else:
     return autoroller.PrepareRoll(args.ignore_checks, args.run_tryjobs)
 
 if __name__ == '__main__':
   sys.exit(main())