Removed unused element parameter.

Not used in hasWillChangeThatCreatesStackingContext.

R=sigbjornf@opera.com

Review URL: https://codereview.chromium.org/269823005

git-svn-id: svn://svn.chromium.org/blink/trunk@173304 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Fix AnimationAnimationPlayerTest.AttachedAnimationPlayers test

Fix AnimationAnimationPlayerTest.AttachedAnimationPlayers test:
it passed empty key value to a hash map (which is unacceptable).

Review URL: https://codereview.chromium.org/268823004

git-svn-id: svn://svn.chromium.org/blink/trunk@173305 bbb929c8-8fbe-4397-9dbb-9b2b20218538