Reproduction steps:
1. Open the attached project "Animation Defaults.zip";
2. Open the "main.unity" scene;
3. Select Canvas->Image 2 object;
4. Observe that his Scale.Y is set to 1.5.
5. Enter a play mode;
6. Observe that the Y value is changed to default value - 1.

Expected results: The default values are based on the instance of the object;
Actual results: The default values are shared across all objects that use the same AnimationController.

Reproduced on: 5.3.5p6, 5.4.1f1, 5.5.0p4, 5.6.0b5