How to reduce shader compilation time on android devices

We are developing VR application wich consists of several small scenes for specific android device (GearVR/Samsung Galaxy S6). Currently scene switching is very slow and profiler shows most of the loading time spent on shader compilation. We want to achieve either fast scene switching or backgroung scene loading without breaking VR experience (so no loading screens with headtracking disabled). Switching scenes with Application.LoadLevelAsync works bad as there are noticeable hickups while loading and total loading time significantly increases. So now we are focusing on reducing loading time of Application.LoadLevel and the main bottleneck here is shader compilation. I've heard about Shader.WarmupAllShaders but as far as I understand it works only within one scene and has nothing to do with switching scenes. So is there a way to speed up scene load? Maybe some way to provide precompiled shaders for application running on specific device? Or should we just use most simple shaders - some of them have compilation time about 120-140ms on Samsung Galaxy S6, is that normal?