Make the scroll_delta flooring behavior the same as before SyncedProperty change

Make the scroll_delta flooring behavior the same as before SyncedProperty change

Impl sents truncated ScrollDelta to main. Recent change to use
SyncedProperty changes the truncation behavior in the case when
scroll_offset(active_base) is non-integer. This CL restores the
behavior.

The whole flooring will be gone soon when we are able to send
non-integer scroll delta to main. This CL is only meant to make
sure that SyncedProperty switch has no functional change.

BUG=

Committed: https://crrev.com/3b4800d42ead0f0ff9420755af741e79613d4a01
Cr-Commit-Position: refs/heads/master@{#314237}

[miletus1, 2015-02-02 22:55:00]

miletus@google.com changed reviewers:
+ aelias@chromium.org

[miletus1, 2015-02-02 22:55:04]

miletus@google.com changed reviewers:
+ miletus@google.com

[aelias_OOO_until_Jul13, 2015-02-02 23:03:10]

lgtm

[miletus1, 2015-02-02 23:23:49]

The CQ bit was checked by miletus@google.com

[commit-bot: I haz the power, 2015-02-02 23:25:07]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/867823007/1

[commit-bot: I haz the power, 2015-02-03 01:36:38]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-03 01:37:27]

Patchset 1 (id:??) landed as
https://crrev.com/3b4800d42ead0f0ff9420755af741e79613d4a01
Cr-Commit-Position: refs/heads/master@{#314237}