To reproduce:
1. Create new project in any applicable Unity version
2. in Hierarchy view, search input field, type anything

Expected: background and irrelevant items turn grey
Actual: background and irrelevant items turn black, massive performance slowdown and leaking memory while moving view port camera

Reproduced in: 2017.1.0b9, 2017.2.0a1, 2017.2.0a2
Not reproduced in: 5.4.5p3, 5.5.4f1, 5.6.0f1, 5.6.1p2, 2017.1.0b8
Regression starts in: 2017.2.0a1 (build #2031)

Note: another bug that occurs is black background appears (instead of grey one) while searching in Hierarchy view (check pictures attached)
Note: memory is only leaking when moving or rotating view port camera in Scene view
Note: also appears in 5.6.1f1, 5.6.1f1, but is fixed in the following version 5.6.1p2
Note: very rarely the bug fails to reproduce