Use FileSystem API to store data in Opera

Our Opera issue turned out to be localStorage size limit. Given that FileSystem API apparently works again in recent Opera versions, it`s best to use FileSystem API and migrate the data. I`ve removed the old migration code while at it, no point keeping it forever.

[Thomas Greiner, 2013-11-25 14:17:23]

LGTM

[Wladimir Palant, 2013-11-26 08:51:50]

Two more issues fixed:

1) First-run page was appearing on update because the data import from
localStorage is asynchronous. The solution was to make the seenDataCorruption
flag trigger first-run page rather than missing currentVersion, this flag can be
reset if we are importing from localStorage.

2) seenDataCorruption flag wasn't always set correctly. The reason is that io.js
loads before background.js. It was setting seenDataCorruption flag synchronously
which might happen earlier than background.js loads and initializes
seenDataCorruption with false. The solution was to use Utils.runAsync() here
which is guaranteed to run the callback when all scripts load.

[Thomas Greiner, 2013-11-26 10:23:32]

LGTM with nits addressed

http://codereview.adblockplus.org/5923900886089728/diff/5930525202055168/lib/...
File lib/filesystem/io.js (right):

http://codereview.adblockplus.org/5923900886089728/diff/5930525202055168/lib/...
lib/filesystem/io.js:77: callback(null)
nit: semicolon missing

http://codereview.adblockplus.org/5923900886089728/diff/5930525202055168/lib/...
File lib/websql/io.js (right):

http://codereview.adblockplus.org/5923900886089728/diff/5930525202055168/lib/...
lib/websql/io.js:65: callback(null)
nit: semicolon missing

[Wladimir Palant, 2013-11-26 10:34:21]

Addressed nits:

https://hg.adblockplus.org/adblockpluschrome/rev/fce28c7eff66 - default branch
https://hg.adblockplus.org/adblockpluschrome/rev/7c03cefed8f1 - 1.6.x branch

[Wladimir Palant, 2013-11-26 12:37:35]

I had to partially revert the previous change and to introduce a new flag to
prevent the first-run actions. With the previous solution, the first-run actions
would still run on update - while seenDataCorruption flag wasn't set, the
extension version number changed and no filter subscription was present.

[Thomas Greiner, 2013-11-26 13:40:12]

http://codereview.adblockplus.org/5923900886089728/diff/6220332415320064/back...
File background.js (right):

http://codereview.adblockplus.org/5923900886089728/diff/6220332415320064/back...
background.js:57: if (!importingOldData)
You're only using this variable for this check here so you don't need
importingOldData to be a global variable. By making it the return value of
importOldData you could make it a local variable.

[Wladimir Palant, 2013-11-27 15:46:21]

http://codereview.adblockplus.org/5923900886089728/diff/6220332415320064/back...
File background.js (right):

http://codereview.adblockplus.org/5923900886089728/diff/6220332415320064/back...
background.js:57: if (!importingOldData)
On 2013/11/26 13:40:13, Thomas Greiner wrote:
> You're only using this variable for this check here so you don't need
> importingOldData to be a global variable. By making it the return value of
> importOldData you could make it a local variable.

Done.

[Felix Dahlke, 2013-11-27 16:32:38]

LGTM

[Thomas Greiner, 2013-11-27 16:49:39]

LGTM