IDL compiler: sync Python to r165324

Python side to:
[GenerateVisitDOMWrapper] should use SetReferenceFromGroup instead of SetObjectGroupId
https://codereview.chromium.org/116093008

BUG=239771
TBR=haraken
NOTRY=true

Review URL: https://codereview.chromium.org/141713003

git-svn-id: svn://svn.chromium.org/blink/trunk@165374 bbb929c8-8fbe-4397-9dbb-9b2b20218538