Web Animations: Clean up EventDelegate in notifyElementDestroyed

The EventDelegate held on TimedItem might still be pointing to the Element
which we've just destroyed, so we should clear this too.

BUG=364066

Review URL: https://codereview.chromium.org/240283008

git-svn-id: svn://svn.chromium.org/blink/trunk@171851 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Handle the DOMString case of CRC2D.fillStyle/strokeStyle correctly

Non-CanvasGradient/CanvasPattern objects would not be ToString(v)'d and
have the result assigned/parsed as a color-string.
Implement this by checking for CanvasGradient/CanvasPattern first,
and then invole ToString() on the value.

BUG=364008

Review URL: https://codereview.chromium.org/237743007

git-svn-id: svn://svn.chromium.org/blink/trunk@171852 bbb929c8-8fbe-4397-9dbb-9b2b20218538