[Sync] Remove backend unrecoverable error handler

[Sync] Remove backend unrecoverable error handler

It was being used to allowed passing ownership of an error handler, but passing
a weak handle works just as well.

BUG=511235
Committed: https://crrev.com/e1c3d02433227b589fad049928b8a70157e9aecf
Cr-Commit-Position: refs/heads/master@{#342384}

[Nicolas Zea, 2015-08-05 22:36:35]

zea@chromium.org changed reviewers:
+ maxbogue@chromium.org

[Nicolas Zea, 2015-08-05 22:36:35]

+Max, PTAL. This is basically a whole lot of plumbing of WeakHandles around.

[maxbogue, 2015-08-05 23:23:56]

lgtm assuming bots pass. I haven't seen WeakHandles before; neat, and a nice
solution to this problem.

[Nicolas Zea, 2015-08-06 21:05:50]

zea@chromium.org changed reviewers:
+ pavely@chromium.org

[Nicolas Zea, 2015-08-06 21:05:51]

+Pavel for committer review

[pavely, 2015-08-06 21:08:17]

rs lgtm

[Nicolas Zea, 2015-08-06 21:11:59]

The CQ bit was checked by zea@chromium.org

[commit-bot: I haz the power, 2015-08-06 21:13:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1275743002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1275743002/20001

[commit-bot: I haz the power, 2015-08-06 21:16:13]

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

[commit-bot: I haz the power, 2015-08-06 21:16:14]

Try jobs failed on following builders:
  linux_chromium_compile_dbg_32_ng on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)
  ios_dbg_simulator_ninja on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios_dbg_simulator...)
  ios_rel_device_ninja on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios_rel_device_ni...)
  mac_chromium_compile_dbg_ng on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_comp...)
  mac_chromium_rel_ng on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_rel_...)

[Nicolas Zea, 2015-08-06 22:27:28]

The CQ bit was checked by zea@chromium.org

[Nicolas Zea, 2015-08-06 22:27:28]

The patchset sent to the CQ was uploaded after l-g-t-m from
maxbogue@chromium.org, pavely@chromium.org
Link to the patchset: https://codereview.chromium.org/1275743002/#ps40001
(title: "Rebase")

[commit-bot: I haz the power, 2015-08-06 22:29:08]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1275743002/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1275743002/40001

[commit-bot: I haz the power, 2015-08-06 22:46:17]

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

[commit-bot: I haz the power, 2015-08-06 22:46:18]

Try jobs failed on following builders:
  linux_chromium_compile_dbg_32_ng on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)
  linux_chromium_rel_ng on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[Nicolas Zea, 2015-08-06 22:49:19]

The CQ bit was checked by zea@chromium.org

[Nicolas Zea, 2015-08-06 22:49:19]

The patchset sent to the CQ was uploaded after l-g-t-m from
maxbogue@chromium.org, pavely@chromium.org
Link to the patchset: https://codereview.chromium.org/1275743002/#ps60001
(title: "Fix SyncClient")

[commit-bot: I haz the power, 2015-08-06 22:51:18]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1275743002/60001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1275743002/60001

[commit-bot: I haz the power, 2015-08-07 00:24:56]

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

[commit-bot: I haz the power, 2015-08-07 00:24:57]

Try jobs failed on following builders:
  linux_chromium_asan_rel_ng on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[Nicolas Zea, 2015-08-07 16:48:03]

The CQ bit was checked by zea@chromium.org

[Nicolas Zea, 2015-08-07 16:48:04]

The patchset sent to the CQ was uploaded after l-g-t-m from
maxbogue@chromium.org, pavely@chromium.org
Link to the patchset: https://codereview.chromium.org/1275743002/#ps80001
(title: "Fix leak")

[commit-bot: I haz the power, 2015-08-07 16:48:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1275743002/80001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1275743002/80001

[Nicolas Zea, 2015-08-07 16:53:07]

The CQ bit was unchecked by zea@chromium.org

[Nicolas Zea, 2015-08-07 16:54:48]

The CQ bit was checked by zea@chromium.org

[Nicolas Zea, 2015-08-07 16:54:48]

The patchset sent to the CQ was uploaded after l-g-t-m from
maxbogue@chromium.org, pavely@chromium.org
Link to the patchset: https://codereview.chromium.org/1275743002/#ps100001
(title: "Fix leak")

[commit-bot: I haz the power, 2015-08-07 16:54:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1275743002/100001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1275743002/100001

[commit-bot: I haz the power, 2015-08-07 18:14:51]

Committed patchset #6 (id:100001)

[commit-bot: I haz the power, 2015-08-07 18:15:30]

Patchset 6 (id:??) landed as
https://crrev.com/e1c3d02433227b589fad049928b8a70157e9aecf
Cr-Commit-Position: refs/heads/master@{#342384}