Implement requestAnimationFrame

Cherry-pick from webkit-org branch on Code Aurora Forum:

requestAnimationFrame doesn't throttle on Mac
https://www.codeaurora.org/gitweb/quic/la/?p=platform/external/webkit.git;a=commit;h=d9dca741b4762c433ae18f7a1bc59a3a81861fc8

Timestamp parameter to requestAnimationFrame is busted in USE(REQUEST_ANIMATION_FRAME_TIMER) path
https://www.codeaurora.org/gitweb/quic/la/?p=platform/external/webkit.git;a=commit;h=f0909a46fa167c84062c63caffef340a6054bc1e

Rename webkitCancelRequestAnimationFrame to webkitCancelAnimationFrame to match spec change
https://www.codeaurora.org/gitweb/quic/la/?p=platform/external/webkit.git;a=commit;h=cd5d11d662d638b3e4dfda33f23cda907f007f12

Remove partially implemented per-Element visibility checks from requestAnimationFrame logic
https://www.codeaurora.org/gitweb/quic/la/?p=platform/external/webkit.git;a=commit;h=9fb90af3cebd0e595990cded0941d230cf77dcc1

(cherry picked from commit 47ff59a279eab9ae5dd1fd17ce7057431750a0b5)

Change-Id: I7e77200006bb0c4cd4b4209082296c425bd207c1