IDL compiler: sync Python to r167001
IDL compiler: sync Python to r167001

Python side to:
Remove isolated world parameters from event listener attributes
https://codereview.chromium.org/149803005/

Nice cleanup!

BUG=239771
TBR=haraken
NOTRY=true

Review URL: https://codereview.chromium.org/162583002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@167063 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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