IDL compiler: sync Python to r167276, r167361

Python side to:
Remove isolatedWorldForEnteredContext() and isolatedWorldForIsolate()
https://codereview.chromium.org/137953010/

...and to un-revert:
Revert 167360 "Revert 167276 "Remove isolatedWorldForEnteredCont..."
https://codereview.chromium.org/171313003

BUG=239771
TBR=haraken
NOTRY=true

Review URL: https://codereview.chromium.org/169193004

git-svn-id: svn://svn.chromium.org/blink/trunk@167387 bbb929c8-8fbe-4397-9dbb-9b2b20218538