Reproduction steps:
1. Open attached project
2. Open and play the "GUILeak" scene
3. There is a "GUILeak" object in the scene that will destroy and recreate object with UI canvas component every frame
4. Check profiler and observe that memory consuption keeps getting higher

NOTE: You can click "Stop Allocations" button on the screen. Memory consumption will stabilize but it will never return to original level.