Make sure to indicate to Chrome when our filters change

See http://developer.chrome.com/extensions/webRequest.html#caching - it seems that we should be calling handlerBehaviorChanged() whenever our filters change.

[Thomas Greiner, 2012-10-29 16:40:16]

Please check if it's possible for a user to somehow trigger multiple triggers
shortly after another that result in handlerBehaviorChanged to be called.

http://codereview.adblockplus.org/8691076/diff/1/webrequest.js
File webrequest.js (right):

http://codereview.adblockplus.org/8691076/diff/1/webrequest.js#newcode35
webrequest.js:35: chrome.webRequest.handlerBehaviorChanged();
according to the docs we shouldn't call it too often
adding multiple filters could make that happen so calling it through a timer
might improve that

example:
- 0:01 filter.added: starts 2s timer
- 0:02 filter.added: clears previous timer, starts 2s timer
- 0:04 timer fires and calls handlerBehaviorChanged()

it might not make sense, though, if there is no way in the application that such
notifications are being dispatched that quickly

[Wladimir Palant, 2012-10-30 09:52:02]

Ok, I've added a delay.

[Thomas Greiner, 2012-10-30 10:17:22]

one quick change left

http://codereview.adblockplus.org/8691076/diff/1002/webrequest.js
File webrequest.js (right):

http://codereview.adblockplus.org/8691076/diff/1002/webrequest.js#newcode47
webrequest.js:47: window.setTimeout(onFilterChange, 2000);
set onFilterChangeTimeout variable
otherwise it will always be null

[Wladimir Palant, 2012-10-30 10:41:08]

Heh, I wonder why it seemed to work when I tested it.

[Thomas Greiner, 2012-10-30 10:47:37]

On 2012/10/30 10:41:08, Wladimir Palant wrote:
> Heh, I wonder why it seemed to work when I tested it.

because it called the handlerBehaviorChanged function (as it did before) but
this time with a 2s delay

so in comparison to my example (see one of the previous comments) it would have
looked like that:
- 0:01 filter.added: starts 2s timer
- 0:02 filter.added: starts 2s timer
- 0:03 timer fires and calls handlerBehaviorChanged()
- 0:04 timer fires and calls handlerBehaviorChanged()

[Thomas Greiner, 2012-10-30 10:47:59]

LGTM