How to reproduce:
1. Open the attached "LoadSceneAsync" project
2. Switch to Android platform and deploy to Android device (File --> Build settings --> Build & Run)
3. Once Application is loaded, press "Load" ant observe the total scene load time (You can press "Load" multiple times, to see that the results are more or less consistent)

Expected result: It is around ~30ms as in 2017.2.0a1 and earlier versions
Actual result: Is is around ~60ms in 2017.2.0a2 and later versions

Regression introduced in - 2017.2.0a2
Reproducible with - 2018.2.0a1, 2017.3.1p2, 2017.2.2f1, 2017.2.0a2
Not reproducible with - 2017.2.0a1, 2017.1.3p1

DUT:
Google Pixel 2 XL*, OS:8.1.0, CPU:arm64-v8a, GPU:Adreno (TM) 540, Build:google/taimen/taimen:8.1.0/OPM1.171019.018/4518263:user/release-keys
Samsung SM G950U*, OS:7.0, CPU:arm64-v8a, GPU:Adreno (TM) 540, Build:samsung/dreamqltesq/dreamqltesq:7.0/NRD90M/G950USQU1AQC8:user/release-keys
Xiaomi MI 5s*, OS:6.0.1, CPU:arm64-v8a, GPU:Adreno (TM) 530, Build:Xiaomi/capricorn/capricorn:6.0.1/MXB48T/V8.0.10.0.MAGCNDH:user/release-keys

By design --> Before Unity 2017.2.0a2 we had 60 fps by default - resulting in 33 ms. After 2017.2.0a2 we are having default - 30 fps, with 2 frames being 67 ms.