Fixed Sync does not appear to recover from network outage

[alexwykoff]

Old title: Sync does not appear to recover from network outage #7972 (comment)

Test plan

#8108 (comment)

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• Did you search for similar issues before submitting this one?
  Yes

• Describe the issue you encountered:
  If the network is disconnected and Brave is left open, sync will not reconnect and update appropriately.

• Platform (Win7, 8, 10? macOS? Linux distro?):
  Tested on OS X

• Brave Version (revision SHA):
  0.14.0 RC2 (b00c5d9)

• Steps to reproduce:

  1. Use a clean profile on two machines
  2. Create a new sync group on machine1
  3. Join the sync group on machine2
  4. Turn off the network for machine2
  5. Add a bookmark and a bookmark folder on machine1
  6. Turn on the network for machine2
  7. Wait a reasonable amount of time (5 minutes I believe was the schedule, but I did 20 for good measure)

• Actual result:
  The bookmark, bookmark folder, and history are not synced, even if history sync is turned on later

• Expected result:
  Sync should retry periodically and when the network is available, resume sync functionality.

• Will the steps above reproduce in a fresh profile? If not what other info can be added?
  Yes

• Is this an issue in the currently released version?
  Not sure

• Can this issue be consistently reproduced?
  Yes

• Extra QA steps:
  1.
  2.
  3.

• Screenshot if needed:

• Any related issues:

[diracdeltas]

how long did you wait between steps 3 and 4?

i would expect sync to fail silently until restart if the network is disconnected before registration is done (in fact i have seen this before). however, if registration is done, it should be retrying on network failure. cc @ayumi