[DevTools] Hide popover on window resize.

Popover is a modal element, and should be hidden on resize,
toggling fullscreen, zoom change akin to TextPrompt.

BUG=388659

Review URL: https://codereview.chromium.org/353833003

git-svn-id: svn://svn.chromium.org/blink/trunk@177092 bbb929c8-8fbe-4397-9dbb-9b2b20218538