The reason why the icon was reset to default state every time is because I called setIcon
before the tab finishes loading and obtains "complete" state.
I guess there should be some information about this in documentation on tabs or on browser actions, but I didn't find it: the default icon is actually applied - by-design - to a specific page after it finishes loading. I moved the call setIcon
into tabs.onUpdated
handler, and now custom icon persists.
This contradicts to my former understanding that the browser action icon is set on a per tab basis, regarless to a page loaded into the tab and its state.
@KonradDzwinel kindly provided a simple extension to test the case (look at the comments). I changed its background.js script to demonstrate this behaviour:
chrome.browserAction.onClicked.addListener(function(tab)
{
chrome.browserAction.setIcon({path: 'gfx/icon2.png', tabId: tab.id});
});
To reproduce this behaviour, on any tab press the browser action icon to get it changed. Then refresh the page. As a result the browser action icon reset back to default.
If this behaviour is explained in some documentation, please, write this in comments, and I'll update the answer. From what I have read so far, I was convinced that default icon is set for new tab at its creation time, and then any changes to it are solely under extension's control.