[DevTools] Improve modal elements handling.

Dialogs now have injected modalHostView.
SuggestBox and Popover are dismissed on blur and resize.

BUG=344307

Review URL: https://codereview.chromium.org/169623004

git-svn-id: svn://svn.chromium.org/blink/trunk@167700 bbb929c8-8fbe-4397-9dbb-9b2b20218538