Use StrictTypeChecking on EME objects.

With StrictTypeChecking, invalid types, null, etc. cannot reach the C++ code.

BUG=224791

Review URL: https://codereview.chromium.org/239083003

git-svn-id: svn://svn.chromium.org/blink/trunk@171878 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: make counters graph hidpi-friendly.

Review URL: https://codereview.chromium.org/239703013

git-svn-id: svn://svn.chromium.org/blink/trunk@171879 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove showRepaintCounter setting. It's never set and doesn't do anything.

Review URL: https://codereview.chromium.org/241153002

git-svn-id: svn://svn.chromium.org/blink/trunk@171880 bbb929c8-8fbe-4397-9dbb-9b2b20218538
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: svn://svn.chromium.org/blink/trunk@171881 bbb929c8-8fbe-4397-9dbb-9b2b20218538