How to enable full screen compose window in Gmail

Google recently introduced fullscreen centered compose window for Gmail, lets you enable full screen compose window to your Gmail account instead of small compose window which is shows right side of the screen.
How to Enable:

• Open Gmail.com and sign in to your account
• Click on the compose button
• Then click small arrow icon in the compose window next to Discard draft icon
• Next click Default to full-screen option in the menu shows below image

• Then close the older compose window and open it again

Now you can see the full screen compose window instead of small window.