Put newly allocated buffers at the right end of the buffers list

Put newly allocated buffers at the right end of the buffers list

If a major gc happens between allocation and initialization of the
buffer, it might be already in old space. Since we need the list of
buffers to be sorted from new to old, we keep track of the last buffer
and put old buffers to the end

BUG=chromium:476032
R=hpayer@chromium.org,dslomov@chromium.org
LOG=n

Committed: https://crrev.com/05ed6cb6b922e428d70c15c6d5b97aacde84887c
Cr-Commit-Position: refs/heads/master@{#27811}

[jochen (gone - plz use gerrit), 2015-04-13 15:40:11]

ptal

[Hannes Payer (out of office), 2015-04-14 09:22:06]

lgtm

[jochen (gone - plz use gerrit), 2015-04-14 09:24:35]

The CQ bit was checked by jochen@chromium.org

[commit-bot: I haz the power, 2015-04-14 09:24:47]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1079923003/1

[commit-bot: I haz the power, 2015-04-14 09:26:17]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-14 09:26:30]

Patchset 1 (id:??) landed as
https://crrev.com/05ed6cb6b922e428d70c15c6d5b97aacde84887c
Cr-Commit-Position: refs/heads/master@{#27811}