Steps to reproduce:
1. Open QA-supplied project
2. Open Scene "test"
3. Enter Play Mode

Expected: Content gets distributed within the bounds
Actual: Content exits the bounds

Reproduced in: 2018.2.0a1, 2018.2.0f2, 2018.3.0a5
Not reproduced in: 2017.1.4p2, 2017.2.3p2, 2017.3.2f1, 2017.4.7f1, 2018.1.9f1

Note: the screenshot with the content in the top right corner is prior to 2018.2 and the content that is out of bounds is post-2018.2

Hard to say if this is a bug since prior to 2018.2 there was an issue as well because the content was in the top right corner and ignored ForceRebuildLayoutImmediate at the Start of the scene, but the content was put in order when the user pressed Ctrl+R

Post-2018.2 the layout stays the same, ignoring the bounds, even if you press Ctrl+R