Upgrade to storage.sync API, so we can synchronize Vimium settings across computers

[smblott-github]

Addresses #604.

[philc]

Nice, thank you @smblott-github for building this out and for leaving embedded refactor comments so I can follow your changes. Long time coming.

I haven't looked closely yet at understanding the full impact, but can you comment on the risk of this change? Will it break existing users' settings? Have you see any annoying behavior/conflicts when syncing across multiple computers?

[smblott-github]

Hi @philc .

This was written a long time ago. And Travis seems to be failing now. I'm sure it can be easily patched up.

"Will it break existing users' settings?":

• It is possible. If you have two chrome/vimium instances both logged into the same account, but with different vimium settings, you end up with the settings from one or the other. Specifically, the shared settings are those from the first instance on which you click "save" on the options page. That's what triggers syncing.

"Have you see any annoying behavior/conflicts when syncing across multiple computers?"

• No. None at all. I might have said this before, but this is in my "Could not live without" box.
• Better still, I got a new laptop recently. Fired it up, and vimium had all my bindings and other settings configured out of the box.

If you're interested in this (and are happy with the approach), then I'd happily work on brinking it up to date.

[philc]

Black line is unnecessary

[philc]

Stephen, your approach looks good to me. Once the code is updated we should ship it in the next vimium release.

[smblott-github]

OK. I'll work on it.

[smblott-github]

My work on this is now over at #1029.

[philc]

Closing in favor of #1029