bisect-builds.py: Save cache in parent scope

tools/bisect-builds.py

 #!/usr/bin/env python
 # Copyright (c) 2012 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.
 
 """Snapshot Build Bisect Tool
 
 This script bisects a snapshot archive using binary search. It starts at
 a bad revision (it will try to guess HEAD) and asks for a last known-good
 revision. It will then binary search across this revision range by downloading,
@@ skipping 426 matching lines @@
     # The cache is stored in the same directory as bisect-builds.py
     cache_filename = os.path.join(
         os.path.abspath(os.path.dirname(__file__)),
         '.bisect-builds-cache.json')
     cache_dict_key = self.GetListingURL()
 
     def _LoadBucketFromCache():
       if self.use_local_cache:
         try:
           with open(cache_filename) as cache_file:
-            cache = json.load(cache_file)
+            for (key, value) in json.load(cache_file).items():
+              cache[key] = value
             revisions = cache.get(cache_dict_key, [])
             githash_svn_dict = cache.get('githash_svn_dict', {})
             if revisions:
               print 'Loaded revisions %d-%d from %s' % (revisions[0],
                   revisions[-1], cache_filename)
             return (revisions, githash_svn_dict)
         except (EnvironmentError, ValueError):
           pass
       return ([], {})
 
@@ skipping 817 matching lines @@
 
     print 'CHANGELOG URL:'
     if opts.official_builds:
       print OFFICIAL_CHANGELOG_URL % (min_chromium_rev, max_chromium_rev)
     else:
       PrintChangeLog(min_chromium_rev, max_chromium_rev)
 
 
 if __name__ == '__main__':
   sys.exit(main())