Oilpan: revert page navigation count GCing.

Oilpan: revert page navigation count GCing.

The inclusion of https://codereview.chromium.org/1353283002 as
part of r350775 was not intentional - back it out.

We want to land some variation of this now, but not in this form.

R=haraken
BUG=534524
Committed: https://crrev.com/d9e8f44fe594dcd9c4e2378637e4bee567ff9ccb
Cr-Commit-Position: refs/heads/master@{#350806}

[sof, 2015-09-25 09:55:53]

The CQ bit was checked by sigbjornf@opera.com to run a CQ dry run

[commit-bot: I haz the power, 2015-09-25 09:56:12]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1369683003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1369683003/1

[sof, 2015-09-25 09:57:21]

sigbjornf@opera.com changed reviewers:
+ oilpan-reviews@chromium.org

[sof, 2015-09-25 09:57:22]

please take a look.

My apologies, landing this part shouldn't have happened.

[haraken, 2015-09-25 09:59:55]

LGTM

[commit-bot: I haz the power, 2015-09-25 11:26:23]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-09-25 11:26:24]

Dry run: This issue passed the CQ dry run.

[sof, 2015-09-25 11:34:23]

The CQ bit was checked by sigbjornf@opera.com

[commit-bot: I haz the power, 2015-09-25 11:34:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1369683003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1369683003/1

[commit-bot: I haz the power, 2015-09-25 11:39:16]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-25 11:40:27]

Patchset 1 (id:??) landed as
https://crrev.com/d9e8f44fe594dcd9c4e2378637e4bee567ff9ccb
Cr-Commit-Position: refs/heads/master@{#350806}