Chrome web app gives the native app feels for website. You can create a web app for any website on the Internet.
Step 1 : You need to create a plain text file with the following contents. Rename/edit the contents as per your web app.

{  
 "name": "App Name",  
 "description": "App description (132 characters or less, no HTML)",  
 "version": "1.0.0",  
 "manifest_version": 2,  
 "icons": {  
 "128": "icon_128.png"  
 },  
 "app": {  
 "urls": [  
 "http://www.justunfollow.com/"  
 ],  
 "launch": {  
 "web_url": "http://www.justunfollow.com/"  
 }  
 }  
 }

Step 2 : Saved the file, renaming it to “manifest.json” (make sure the .txt file extension is gone).

Step 3 :  In this same folder, download/create an icon for the app (it needs to be a 128×128 PNG file), rename it “icon\_128.png”.

Step 4 :  Open the ‘Extensions’ page from Chrome’s Settings menu.  Tick “Developer Mode”. Click “Load Unpacked Extension” and select the web app folder.

Step 5 : Your app will be available at Chrome app section. 


Source : <http://www.omgchrome.com/how-to-create-a-chrome-web-app/>