Steps to reproduce:

1) Create a new project.
2) Add any UI element ( tested with Text and Image).
3) Enable Development Build and Autoconnect Profiler.
4) Build and run project on a device.
5) After game will be loaded, you will notice that EventSystem.Update() been loaded on the first frame (check profiler).
6) Click anywhere on the screen and you will notice that its been called again and takes a lot of memory (check profiler).(see attached image 'bug.png').

Expected result: EventSystem.Update() should not cause a big spike after screen been touched first time.
Actual result: It causes a big spike after screen been touched first time.

Reproduced with: 5.3.6p3, 5.4.0p2, 5.5.0b1.

Not reproduced with: 5.2.4f1.