Scrollbar doesn't cover entire text at the bottom.
Steps to reproduce:
1. Open attached repro project named "Repro scrollbar".
2. Select "TestObject" object in hierarchy menu.
3. Try scrolling down the "Content" box in the Inspector.
4. It doesn't scroll down to the very bottom of the text box.
--- Note that you won't see "You will not see this text in the Content menu" text in the content menu even tough it exist as you can see in the attached photo.

Attached photo link: https://gyazo.com/bdc956f86040e18ab2965c07a7ebb5bd

Reproduced in: 5.3.2f1 and 5.4.0b20