Implement Android key/value backup

Implement Android key/value backup

This replaces our previous impmentation of (Dolly) Auto Backup.
Only the preferences needed to restore the user's signin atate
and sync state are backed up.

BUG=661188
Review-Url: https://codereview.chromium.org/2496693002
Cr-Commit-Position: refs/heads/master@{#432517}
(cherry picked from commit d56b7ec3e6e6c3236835414584f4205283beb218)

Committed: https://chromium.googlesource.com/chromium/src/+/9dd9283bac8aa9908d6868a052e088a9839499b4

[aberent, 2016-11-17 11:40:45]

Description was changed from

==========
Implement Android key/value backup

This replaces our previous impmentation of (Dolly) Auto Backup.
Only the preferences needed to restore the user's signin atate
and sync state are backed up.

BUG=661188

Review-Url: https://codereview.chromium.org/2496693002
Cr-Commit-Position: refs/heads/master@{#432517}
(cherry picked from commit d56b7ec3e6e6c3236835414584f4205283beb218)
==========

to

==========
Implement Android key/value backup

This replaces our previous impmentation of (Dolly) Auto Backup.
Only the preferences needed to restore the user's signin atate
and sync state are backed up.

BUG=661188

Review-Url: https://codereview.chromium.org/2496693002
Cr-Commit-Position: refs/heads/master@{#432517}
(cherry picked from commit d56b7ec3e6e6c3236835414584f4205283beb218)

Committed:
https://chromium.googlesource.com/chromium/src/+/9dd9283bac8aa9908d6868a052e0...
==========

[aberent, 2016-11-17 11:40:46]

Committed patchset #1 (id:1) manually as
9dd9283bac8aa9908d6868a052e088a9839499b4.

[amineer_google, 2016-11-18 03:31:18]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/2509323004/ by amineer@google.com.

The reason for reverting is: Breaks build.  Please don't reland.

https://uberchromegw.corp.google.com/i/official.android.continuous/builders/b....