Minecraft window automatically resized when making it half sized

I watch Gameplay videos while playing Minecraft and play with a half sized screen.

When I click out of minecraft to pause the video and click back into minecraft the window is forcibly resized to its default setting

Steps to Reproduce:
1. On a Windows 7 computer pull your minecraft window to the left or right side of the screen. It will automatically resize to cover half of the screen.
2. Click outside onto another window or the desktop
3. Click back into the Minecraft window and it will automatically resize back to its default size.