Move ExperimentalWebSocket flag to RuntimeEnabledFeatures, Part 1

Move ExperimentalWebSocket flag from Settings to RuntimeEnabledFeatures to
enable it in LayoutTests.
Note: In this CL, the flag is not enabled in LayoutTests.
It is OK, This is just a preparation.

BUG=275459

Review URL: https://codereview.chromium.org/145553011

git-svn-id: svn://svn.chromium.org/blink/trunk@165827 bbb929c8-8fbe-4397-9dbb-9b2b20218538
IDL compiler: Fix [StrictTypeChecking] for EventHandler and EventListener

Minor CL: fixes to Python CG, one formatting change to Perl.

Following the move of [StrictTypeChecking] to interface,
there was a typo in the Python (should've been is_wrapper_type(),
not is_interface_type), and we now need to list EventHandler as a non-wrapper
type (since it's present on interfaces):
Perl and Python lists of non-wrapper types now agree.

Followup to:
Move [StrictTypeChecking] to interface (from members), where possible
https://codereview.chromium.org/146423002/

BUG=239771
R=haraken

Review URL: https://codereview.chromium.org/148033002

git-svn-id: svn://svn.chromium.org/blink/trunk@165828 bbb929c8-8fbe-4397-9dbb-9b2b20218538