Remove unused imports in webkitpy.

third_party/WebKit/Tools/Scripts/webkitpy/common/net/buildbot/buildbot.py

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 import json
-import operator
 import re
 import urllib
 import urllib2
 
 import webkitpy.common.config.urls as config_urls
 from webkitpy.common.memoized import memoized
 from webkitpy.common.net.layouttestresults import LayoutTestResults
 from webkitpy.common.net.networktransaction import NetworkTransaction
 from webkitpy.common.system.logutils import get_logger
 from webkitpy.thirdparty.BeautifulSoup import BeautifulSoup
@@ skipping 350 matching lines @@
 
             builders_succeeded_in_past = set()
             for past_revision in revisions_in_order[i:]:
                 if not revision_statuses[past_revision]:
                     break
                 builders_succeeded_in_past = builders_succeeded_in_past.union(revision_statuses[past_revision])
 
             if len(builders_succeeded_in_future) == len(builder_revisions) and len(builders_succeeded_in_past) == len(builder_revisions):
                 return revision
         return None