Web Animations CSS: Support 'none' keyword in -webkit-animation-name

CSS animations update did not support "null" animations, instead crashes.
This patch fixes this issue.

Adds test for crash:
virtual/web-animations-css/animations/animation-name-none.html

Fixes crashing tests:
virtual/web-animations-css/animations/animation-shorthand-name-order.html
virtual/web-animations-css/animations/animation-shorthand-removed.html

Review URL: https://chromiumcodereview.appspot.com/22573006

git-svn-id: svn://svn.chromium.org/blink/trunk@155853 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Treat non-callable input as null for EventHandler attributes

Treat non-callable input as null for EventHandler attributes to match the
specification:
http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#eventhandler
http://dev.w3.org/2006/webapi/WebIDL/#TreatNonCallableAsNull

This makes us in line with Firefox and closer to IE10. IE10 will not call
the callback if the input is an object with an handleEvent() method. However,
IE10 will not treat it as null and the value of the EventHandler attribute
will be set to that object.

BUG=269520

Review URL: https://chromiumcodereview.appspot.com/22687002

git-svn-id: svn://svn.chromium.org/blink/trunk@155854 bbb929c8-8fbe-4397-9dbb-9b2b20218538