Periodically remove old pending navigation entries.

Periodically remove old pending navigation entries.

The ReadyToCommitNavigation() callback is used to remove entries from
|pending_navigation_data_use_map_|. However, there are a number of race
conditions which make this callback unreliable until PlzNavigate is
used. This cl periodically deletes navigation entries older than a
threshold that have finished data use.

BUG=660065

[Not at Google. Contact bengr, 2016-11-16 23:54:20]

The CQ bit was checked by kundaji@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-11-16 23:55:31]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-11-17 00:35:22]

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

[commit-bot: I haz the power, 2016-11-17 00:35:22]

Dry run: Try jobs failed on following builders:
  cast_shell_linux on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/cast_shell_linu...)
  chromeos_x86-generic_chromium_compile_only_ng on
master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromeos_x86-ge...)
  linux_chromium_compile_dbg_ng on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)
  linux_chromium_rel_ng on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[Not at Google. Contact bengr, 2016-11-17 16:56:35]

The CQ bit was checked by kundaji@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-11-17 16:57:00]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-11-17 18:12:49]

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

[commit-bot: I haz the power, 2016-11-17 18:12:50]

Dry run: Try jobs failed on following builders:
  linux_android_rel_ng on master.tryserver.chromium.android (JOB_FAILED,
https://build.chromium.org/p/tryserver.chromium.android/builders/linux_androi...)

[Not at Google. Contact bengr, 2016-11-17 21:21:14]

The CQ bit was checked by kundaji@chromium.org to run a CQ dry run

[Not at Google. Contact bengr, 2016-11-17 21:21:40]

Patchset #2 (id:20001) has been deleted

[commit-bot: I haz the power, 2016-11-17 21:22:38]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-11-17 21:29:22]

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

[commit-bot: I haz the power, 2016-11-17 21:29:23]

Dry run: Try jobs failed on following builders:
  ios-simulator on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-simulator/bui...)

[Not at Google. Contact bengr, 2016-11-17 21:37:53]

Patchset #2 (id:40001) has been deleted

[Not at Google. Contact bengr, 2016-11-17 21:38:19]

The CQ bit was checked by kundaji@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-11-17 21:39:48]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-11-18 00:55:26]

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

[commit-bot: I haz the power, 2016-11-18 00:55:27]

Dry run: This issue passed the CQ dry run.