Just like Pocket chrome app does it, where when you save a page, it shows a drag down/popup that shows that you've added the link to Pocket.
How is it possible to achieve something similar?
To give a visual example: 
Just like Pocket chrome app does it, where when you save a page, it shows a drag down/popup that shows that you've added the link to Pocket.
How is it possible to achieve something similar?
To give a visual example: 
 
    
    You can use Programmatic Injection to inject and execute some JS code that modifies the web-pages DOM apropriately.
// In `background.js`:
...
var jsCode = [
    "var div = document.createElement('div');",
    "div.innerHTML = '...';",
    "div.style.position = 'fixed';",
    "div.style.zIndex = '9999';",
    "document.body.appendChild(div);"
].join("\n");
function injectPopover(tabId) {
    chrome.tabs.executeScript(tabId, {
        code: jsCode
    });
}
You will, also, need to set the necessary permissions in your menifest.json depending on when/how you want your popover to be triggered (and on what web-pages).
If you are not familiar with the basic concepts of Chrome Extensions, the Getting-Started Guide it the place to...start.
