cc: Move animate steps from proxies to LayerTreeHostImpl.

cc: Move animate steps from proxies to LayerTreeHostImpl.

Currently both proxies have early outs and call a few methods on
LayerTreeHostImpl to do animations.

This moves it all into a single Animate() call and consolidates the
code in LayerTreeHostImpl.

The old Animate() method took the current frame_time as an argument,
but instead it can use it directly from the BeginFrameArgs. This
required changes LayerTreeHostImpl tests that call Animate() to
start/end impl frames to change the current frame time (which is
more realistic).

R=ajuma
BUG=522658
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Committed: https://crrev.com/12e2f6e4d40560f94d688e6969eb5d9358ead6e3
Cr-Commit-Position: refs/heads/master@{#344351}

[ajuma, 2015-08-19 21:05:03]

lgtm

https://codereview.chromium.org/1297363004/diff/20001/cc/trees/layer_tree_hos...
File cc/trees/layer_tree_host_impl.cc (right):

https://codereview.chromium.org/1297363004/diff/20001/cc/trees/layer_tree_hos...
cc/trees/layer_tree_host_impl.cc:426: // TODO(ajuma): Does this break things if
first commit has an animation?
I suspect it will if break things if we move post-commit animation to happen
right after commit rather than right before we draw. I think the right fix (in a
later CL) is to remove this early-out.

https://codereview.chromium.org/1297363004/diff/20001/cc/trees/layer_tree_hos...
cc/trees/layer_tree_host_impl.cc:447: // TODO(ajuma): Left-overs from
now-deleted background ticking?
Sure looks like it.

[danakj, 2015-08-19 21:07:25]

The CQ bit was checked by danakj@chromium.org

[commit-bot: I haz the power, 2015-08-19 21:08:50]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1297363004/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1297363004/20001

[commit-bot: I haz the power, 2015-08-19 22:25:51]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-08-19 22:27:09]

Patchset 2 (id:??) landed as
https://crrev.com/12e2f6e4d40560f94d688e6969eb5d9358ead6e3
Cr-Commit-Position: refs/heads/master@{#344351}