Refactoring: Add toWebFrameImpl() interface.

We should avoid static_cast at various places by using proper conversion function. This would avoid the error that can be introduced with each manual addition of static_cast addition. Unlike other toClassName functions (like in rendering), we do not require an assertion to confirm the type of passed WebFrame object, since WebFrameImpl is the only child class of WebFrame.

BUG=NONE
TEST=none; no behavior changes.

Review URL: https://chromiumcodereview.appspot.com/23671002

git-svn-id: svn://svn.chromium.org/blink/trunk@156825 bbb929c8-8fbe-4397-9dbb-9b2b20218538
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