Remove setOpenedByDOM calls in CreateWindow.cpp.
Remove setOpenedByDOM calls in CreateWindow.cpp.

They are now redundant with calls in Chromium code, as
of https://codereview.chromium.org/212703005

BUG=357579

Review URL: https://codereview.chromium.org/224173007

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@171881 bbb929c8-8fbe-4397-9dbb-9b2b20218538

primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs