Mainly a fix for Slimjet users.
A user reported that the go back to last active tab function is not working as expected but no matter how I tried I cannot reproduce the problem. Its because the user was using another browser called Slimjet which is based on Chrome but with added function. So when reporting problems do state if you use a different browser as I only test with Chrome stable and Opera.
The problem is Slimjet's 'drag link to open tab' function triggering the chrome.tabs.onActivated event twice and writing both active and last active values to be the same. Solved by checking the tabId first to prevent writing the same value again.
As I tested with Slimjet I notice a strange behaviour with their proprietary new tab page (NTP). When I do an address bar search from the NTP the tab ID will change, that does not happen in Chrome. This behaviour causes SimpleTabOrder just place the next new tab right at the end as it wasn't aware of the tab ID change. Solve by rebuilding the tab map on chrome.tabs.onActivated as well.
Also I went on to fix a minor 'number to integer' warning.
Nothing breaking for Opera so this will be a Chrome only release.