Issue 375 - Make context menus per page

The context menus are hidden/shown globally, when a page is loaded dependent on whether Adblock Plus is active on that page. So when you switch from a page with Adblock Plus enabled to a page with Adblock Plus disabled, the context menu entry still shows up, and vice versa. In order to fix this, I made context menus per page, similar to browserActions.

[Wladimir Palant, 2014-04-25 11:35:50]

http://codereview.adblockplus.org/5095280043098112/diff/5629499534213120/chro...
File chrome/ext/background.js (right):

http://codereview.adblockplus.org/5095280043098112/diff/5629499534213120/chro...
chrome/ext/background.js:221: updateContextMenu();
How many unnecessary updates will this trigger when the extension starts up? How
about checking tab.active here? Same for removeAll() below.

http://codereview.adblockplus.org/5095280043098112/diff/5629499534213120/safa...
File safari/ext/background.js (right):

http://codereview.adblockplus.org/5095280043098112/diff/5629499534213120/safa...
safari/ext/background.js:296:
items[event.command].onclick(event.userInfo.srcUrl, page);
Can there be unknown commands, e.g. from the browser itself?

[Sebastian Noack, 2014-04-25 11:48:03]

http://codereview.adblockplus.org/5095280043098112/diff/5629499534213120/chro...
File chrome/ext/background.js (right):

http://codereview.adblockplus.org/5095280043098112/diff/5629499534213120/chro...
chrome/ext/background.js:221: updateContextMenu();
On 2014/04/25 11:35:50, Wladimir Palant wrote:
> How many unnecessary updates will this trigger when the extension starts up?
How
> about checking tab.active here? Same for removeAll() below.

This was considered and addressed by baling out in
updateContextMenu() if there is already a pending update.

http://codereview.adblockplus.org/5095280043098112/diff/5629499534213120/safa...
File safari/ext/background.js (right):

http://codereview.adblockplus.org/5095280043098112/diff/5629499534213120/safa...
safari/ext/background.js:296:
items[event.command].onclick(event.userInfo.srcUrl, page);
On 2014/04/25 11:35:50, Wladimir Palant wrote:
> Can there be unknown commands, e.g. from the browser itself?

As far as I know the "command" event is only dispatched when a custom context
menu entry is clicked. I couldn't find any other case in the documentation and
during my tests.

[Wladimir Palant, 2014-04-25 12:07:35]

LGTM