Mouse cursor shows endless loading animation, while cursor is hovered onto game in windowed mode. Animation plays endlessly until you move the mouse, after the first scene of the game is loaded.

To Reproduce:
1. Open Unity, make a new project and create a scene
2. Go to File --> Build Settings
3. Go to Player Settings and Disable "Display Resolution Dialog" and uncheck "Default is Full Screen" tab
4. Build the game and play it
5. While loading quickly hover your cursor onto game, and don't move your mouse anymore

Expected result:
Loading animation is played until the game is loaded.

Actual result:
Loading animation is played after the game is loaded, and only ends when player moves the mouse.

Reproducible with 5.5.0f3, 5.4.3f1.

Not reproducible with 5.3.5f1.

Additional notes: Reproducible with Windows 7. Not reproducible with macOS and Windows 10.

Fixed in: 2017.2.0p1, 2017.3.0b5, 2018,1,0a1