Devtools Animations: Add global animation controls to Styles pane

This change adds the same global controls in the animations pane and puts it in the Styles pane instead. Note this change is hidden by the Animation Inspection experiment flag.

BUG=432368

Review URL: https://codereview.chromium.org/805793005

git-svn-id: svn://svn.chromium.org/blink/trunk@187596 bbb929c8-8fbe-4397-9dbb-9b2b20218538