Delete Vibration feature flag.

Vibration API support was launched as stable in M32.

Review URL: https://codereview.chromium.org/164113002

git-svn-id: svn://svn.chromium.org/blink/trunk@167294 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove DOMWrapperWorld::isIsolatedWorld()

This CL replaces DOMWrapperWorld::isIsolatedWorld() with DOMWrapperWorld::world().

BUG=341032

Review URL: https://codereview.chromium.org/169573002

git-svn-id: svn://svn.chromium.org/blink/trunk@167295 bbb929c8-8fbe-4397-9dbb-9b2b20218538