Reproduction steps:
1) Download and open user's attached project (WaitForPresentAndroid.zip)
2) Build and run "Main.unity" scene on an Android device
3) Attach profiler to launched project
4) When application launches wait 10 seconds and then bring application to background (using home button)
5) While application is in background wait 10 seconds and bring it back to foreground (using application icon in menu)
6) Repeat steps 4 and 5 until you can observe performance regression in Gfx.WaitForPresent
-- Notice that Gfx.WaitForPresent "Time ms" value goes from 7 - 15 ms up to 35 - 50 ms

Reproduced on:
2017.1.0b9, 5.6.1p2, 5.5.3p3, 5.4.5p3, 5.3.8f1

Devices under test:
Reproduced with:
Samsung Galaxy S6 Edge, Android 7.0, GPU: Mali-T760
Samsung Galaxy S5 Neo, Android 6.0, GPU: Mali-T720

Unable to reproduce with:
Samsung Galaxy S7, Android 7.0, GPU: Mali-T880
Samsung Galaxy S7, Android 6.0, GPU: Adreno 530
Sony Xperia Z3, Android 6.0, GPU: Adreno 330

iPad Mini 2 (iOS 9.2.1)

Also did not reproduce on standalone (tested on Windows and MacOS)