Repro steps:
1. Open QA attached project "repro_1127825"
2. Build and Run on a mobile device
3. Touch the Input Field
4. Observe the text at the top of the screen

Visible becomes true at the moment when the keyboard is started to be revealed

5. Touch somewhere on the screen to collapse the keyboard

Notice that Visible becomes false as soon as the keyboard starts collapsing which is correct because it's not fully visible anymore

Actual: TouchScreenKeyboard.visible becomes true at the moment when the keyboard is started to be revealed
Expected: TouchScreenKeyboard.visible becomes true when it is fully visible on the screen as described here: https://docs.unity3d.com/ScriptReference/TouchScreenKeyboard-visible.html

Reproducible with: 2017.4.21f1, 2018.3.7f1, 2019.1.0b4, 2019.2.0a4

Tested and successfully reproduced on these devices:
VLNQA00093, Samsung Galaxy S6 edge (SM-G925F), Android 7.0, CPU: Exynos 7 Octa 7420, GPU: Mali-T760
VLNQA00218, Samsung Galaxy Note9 (SM-N960U), Android 8.1.0, CPU: Snapdragon 845 SDM845, GPU: Adreno (TM) 630
VLNQA00233, Meizu - (PRO 6 Plus), Android 7.0.0, CPU: Exynos 8 Octa 8890, GPU: Mali-T880
VLNQA00034, Lge Nexus 4 (Nexus 4), Android 5.1.1, CPU: Snapdragon S4 Pro APQ8064, GPU: Adreno (TM) 320
VLNQA00003, Razer Razer Phone (Phone), Android 7.1.1, CPU: Snapdragon 835 MSM8998, GPU: Adreno (TM) 540
VLNQA00038, Htc Desire 510 (HTC Desire 510), Android 4.4.3, CPU: Snapdragon 410 MSM8916, GPU: Adreno (TM) 306
VLNQA00024, Xiaomi Mi 5 (MI 5), Android 7.0, CPU: Snapdragon 820 MSM8996, GPU: Adreno (TM) 530
iPhone 8 Plus (iOS 11.0)

Notes:
- Doesn't reproduce consistently on iOS