Steps to reproduce:
1. Open the attached project
2. Open 'Test' scene
3. Enter Play mode
--- Scale of 'GameObject' is (0,0,0)
4. Enable the Animator component
--- Scale of 'GameObject' has returned to it's original state on launch

Expected: Animation with 'Write Defaults' off that does not animate any values should not affect anything.
Actual: Object resets to a state which was set when Animator was initialized.
Reproduced with: 5.4.0b15, 5.3.4p4, 5.2.3p3, 5.1.3p3