badgeText.js

chrome.tabs.onUpdated.addListener(function(tabId, changeInfo) {
	if (changeInfo.status == "complete") {
		chrome.tabs.get(tabId, function(tab) {
			window.setInterval(function() {
				setPageActionIcon(tab);
			}, 1000);

			function setPageActionIcon(tab) {
				var canvas = document.createElement('canvas');
				var img = document.createElement('img');
				img.onload = function() {

					// Draw the background image
					var context = canvas.getContext('2d');
					context.drawImage(img, 0, 2);

					// Draw the badge
					var grd = context.createLinearGradient(0, 10, 0, 19);
					grd.addColorStop(0, 'rgb(255, 100, 100)');
					grd.addColorStop(1, 'rgb(150,  50,  50)');

					context.fillStyle = grd;
					context.fillRect(0, 9, 19, 10);

					context.strokeStyle = 'rgb(255, 255, 255)';
					context.strokeRect(0, 10, 1, 1);
					context.strokeRect(0, 19, 1, 1);
					context.strokeRect(19, 10, 1, 1);
					context.strokeRect(19, 19, 1, 1);

					// Draw some text 
					context.fillStyle = "white";
					context.font = "bold 10px Sans-Serif";
					context.fillText(edits, 2, 17, 17);

					chrome.pageAction.setIcon({
						imageData: context.getImageData(0, 0, 19, 19),
						tabId: tab.id
					});
				};
				img.src = "icon16.png";
			}
		});
	}
});