Repro steps:
1. Open QA attached project "repro_1083649"
2. Expand "Canvas" and then select "InputField" in the Hierarchy
3. Delete some characters from the "Text" field of the "Input Field (Script)" component
4. Observe the Image shrinking to fit the size in both Scene and Game Views
5. Add some characters to the same "Text" field

Expected: The Image expands to fit the size of the text
Actual: The Image doesn't expand

Reproducible with: 2017.4.12f1, 2018.2.10f1, 2018.3.0b3, 2019.1.0a2

Notes:
- Adding characters anywhere behind the last character works
- Saving the Scene/Entering Play Mode re-fits the image correctly
- Editing the text value in the Game View when in Play Mode works correctly