Dashcam (0.1)

background.js

chrome.runtime.onMessage.addListener((req, sender, res) => {

	if (req.message === 'capture') {
		// console.log('chrome.runtime.onMessage.addListener', req, sender, res);

		chrome.tabs.captureVisibleTab(sender.tab.windowId, {format: 'png'}, (image) => {
			// console.log('chrome.tabs.captureVisibleTab', image); // image is base64
			res({image: image});
		});		
	}
	return true;
});

conent.js

// alert('content');

chrome.runtime.sendMessage({message: 'capture'}, (res) => {
	// alert('chrome.runtime.sendMessage');
	var link = document.createElement('a');
	link.download = 'screenshot.png';
	link.href = res.image;
	link.click();
});

manifest.json

{
	"manifest_version": 2,
	"name": "Dashcam",
	"version": "0.1",
	"permissions": ["<all_urls>"],
	"content_scripts": [
		{
			"matches": ["<all_urls>"],
			"js": ["content.js"]
		}
	],
	"background": {
		"scripts": ["background.js"],
		"persistent": false
	}
}