Revert of [sync] Fix decryption failure caused by missing user_key

Revert of [sync] Fix decryption failure caused by missing user_key (patchset #2 id:40001 of https://codereview.chromium.org/2813453004/ )

Reason for revert:
Causing crashes on all platforms

Original issue's description:
> [sync] Fix decryption failure caused by missing user_key
> 
> Recently, a change removed code that populated the user_key field of
> nigori nodes. Clients running code from before this change fail to
> import keys that don't have user_key populated. If a post-change
> client commits a nigori node, a pre-change client will fail to
> subsequently import it.
> This change restores code that populates user_key, but omits code
> that fails the import if the user_key is absent.
> 
> R=pavely@chromium.org
> BUG=707967
> 
> Review-Url: https://codereview.chromium.org/2813453004
> Cr-Commit-Position: refs/heads/master@{#463455}
> Committed: https://chromium.googlesource.com/chromium/src/+/399458cbfa1d8458842e9119e6ad063716c7e66e

TBR=pavely@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=707967
Review-Url: https://codereview.chromium.org/2809853003
Cr-Commit-Position: refs/heads/master@{#463655}
Committed: https://chromium.googlesource.com/chromium/src/+/0dd660b9ba6e4699468c635874da841a25e135a7

[Patrick Noland, 2017-04-11 16:43:04]

The CQ bit was checked by pnoland@chromium.org

[Patrick Noland, 2017-04-11 16:43:04]

Created Revert of [sync] Fix decryption failure caused by missing user_key

[commit-bot: I haz the power, 2017-04-11 16:43:31]

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, 2017-04-11 16:43:31]

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

[commit-bot: I haz the power, 2017-04-11 16:43:32]

No L-G-T-M from a valid reviewer yet.
CQ run can only be started once the patch has received an L-G-T-M from a full
committer.
Even if an L-G-T-M may have been provided, it was from a non-committer,_not_ a
full super star committer.
Committers are members of the group "project-chromium-committers".
Note that this has nothing to do with OWNERS files.

[skym, 2017-04-11 16:44:25]

skym@chromium.org changed reviewers:
+ skym@chromium.org

[skym, 2017-04-11 16:44:26]

lgtm

[Patrick Noland, 2017-04-11 16:44:47]

The CQ bit was checked by pnoland@chromium.org

[commit-bot: I haz the power, 2017-04-11 16:45:30]

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, 2017-04-11 16:46:16]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1491929087628870, "parent_rev":
"8917080a3615f02c2346ec29b56c2931a9b6783b", "commit_rev":
"0dd660b9ba6e4699468c635874da841a25e135a7"}

[commit-bot: I haz the power, 2017-04-11 16:47:11]

Description was changed from

==========
Revert of [sync] Fix decryption failure caused by missing user_key (patchset #2
id:40001 of https://codereview.chromium.org/2813453004/ )

Reason for revert:
Causing crashes on all platforms

Original issue's description:
> [sync] Fix decryption failure caused by missing user_key
> 
> Recently, a change removed code that populated the user_key field of
> nigori nodes. Clients running code from before this change fail to
> import keys that don't have user_key populated. If a post-change
> client commits a nigori node, a pre-change client will fail to
> subsequently import it.
> This change restores code that populates user_key, but omits code
> that fails the import if the user_key is absent.
> 
> R=pavely@chromium.org
> BUG=707967
> 
> Review-Url: https://codereview.chromium.org/2813453004
> Cr-Commit-Position: refs/heads/master@{#463455}
> Committed:
https://chromium.googlesource.com/chromium/src/+/399458cbfa1d8458842e9119e6ad...

TBR=pavely@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=707967
==========

to

==========
Revert of [sync] Fix decryption failure caused by missing user_key (patchset #2
id:40001 of https://codereview.chromium.org/2813453004/ )

Reason for revert:
Causing crashes on all platforms

Original issue's description:
> [sync] Fix decryption failure caused by missing user_key
> 
> Recently, a change removed code that populated the user_key field of
> nigori nodes. Clients running code from before this change fail to
> import keys that don't have user_key populated. If a post-change
> client commits a nigori node, a pre-change client will fail to
> subsequently import it.
> This change restores code that populates user_key, but omits code
> that fails the import if the user_key is absent.
> 
> R=pavely@chromium.org
> BUG=707967
> 
> Review-Url: https://codereview.chromium.org/2813453004
> Cr-Commit-Position: refs/heads/master@{#463455}
> Committed:
https://chromium.googlesource.com/chromium/src/+/399458cbfa1d8458842e9119e6ad...

TBR=pavely@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=707967

Review-Url: https://codereview.chromium.org/2809853003
Cr-Commit-Position: refs/heads/master@{#463655}
Committed:
https://chromium.googlesource.com/chromium/src/+/0dd660b9ba6e4699468c635874da...
==========

[commit-bot: I haz the power, 2017-04-11 16:47:11]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/0dd660b9ba6e4699468c635874da...