IDL compiler: sync Python to r162649

Python side to:
Invoke RefPtr::release in GenerateFunctionCallString where possible
https://codereview.chromium.org/85473006

BUG=239771
NOTRY=true
TBR=haraken

Review URL: https://codereview.chromium.org/98143002

git-svn-id: svn://svn.chromium.org/blink/trunk@162944 bbb929c8-8fbe-4397-9dbb-9b2b20218538