Remove unused wallClockTime API from Blink

Final step to remove wallClockTime API from animation delegate interface.

We are currently removing trying to remove all references to base::Time (wall
clock time) from Chrome/Blink compositor/graphics stack.

This requires multiple two-sided patches. Following the process found at
https://groups.google.com/a/chromium.org/d/msg/chromium-dev/ukaRczAK6t8/0ludyZ1Nu4cJ

The steps are;
 * Adding monotonic only API to Blink's animation delegate interface
   https://codereview.chromium.org/185633002

 * Making the delegate adapter use monotonic only API
   https://codereview.chromium.org/185643002

 * (This Patch) -- Remove the wallClockTime API from Blink/WebKit.
   https://codereview.chromium.org/185393005

BUG=299945
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=168889

[mithro-old, 2014-03-10 01:34:39]

Friendly poke, this CL isn't urgent.

This CL will need to wait for https://codereview.chromium.org/184433007/ to
land, but that should happen soon.

Tim

[abarth-chromium, 2014-03-10 21:20:55]

lgtm

[mithro-old, 2014-03-11 05:07:24]

The CQ bit was checked by mithro@mithis.com

[commit-bot: I haz the power, 2014-03-11 05:07:29]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/mithro@mithis.com/185393005/70001

[commit-bot: I haz the power, 2014-03-11 07:00:59]

Change committed as 168889