Make events propagate to ancestor nodes even if the event target is in disconnected DOM trees.

Fixed the ancient behavior which has been there from WebKit era.
I couldn't find any reason not to fix an event propagation for disconnected DOM trees.
Now blink behaves the same way as other browsers.

BUG=249582

Review URL: https://chromiumcodereview.appspot.com/23037012

git-svn-id: svn://svn.chromium.org/blink/trunk@156826 bbb929c8-8fbe-4397-9dbb-9b2b20218538
CSS Animations: Overhaul interpolation test helper

* expectation checking with fuzzy matching
* timeout when running interactively
* use a single style element and populate the dom in a single transaction

Review URL: https://chromiumcodereview.appspot.com/23469010

git-svn-id: svn://svn.chromium.org/blink/trunk@156827 bbb929c8-8fbe-4397-9dbb-9b2b20218538