Web Animations CSS: Convert HashMap to Vector for storing current animation effect results

Review URL: https://codereview.chromium.org/96323003

git-svn-id: svn://svn.chromium.org/blink/trunk@162934 bbb929c8-8fbe-4397-9dbb-9b2b20218538
CSS Animations and Transitions: Enable the Web Animations engine by default.

BUG=258896

Review URL: https://codereview.chromium.org/96243003

git-svn-id: svn://svn.chromium.org/blink/trunk@162935 bbb929c8-8fbe-4397-9dbb-9b2b20218538