Animation track frames zoom in to max upon resizing Animation window.

Steps to reproduce:
1. Create a new project.
2. Go to > Window > Animation > Animation.
3. Click on Main Camera game object.
4. Click on Create button in the Animation window.
5. Click on 'Save' to save the animation clip.
6. Shrink the animation window till the track window part gets hide then expand it.

Note:
1. Video is attached for the reference.
2. Occurring with both scenarios, docking and undocking animation window.

Actual result:
Animation track frames zoom in to max upon resizing Animation window.

Expected result:
Animation track frames do not zoom-in/zoom-out when window resized.

Reproducible in:
2019.3.0a2, 2019.2.0b1, 2019.1.0f2, 2018.3.0f2, 2018.1.9f1

Environment:
Windows and Mac