IDL compiler: sync Python to r167772
IDL compiler: sync Python to r167772

Python side to:
Add context to generated named and indexed property operations.
https://codereview.chromium.org/163883006

TBR=haraken
BUG=239771
NOTRY=true

Review URL: https://codereview.chromium.org/179553007

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@167843 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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