uiautomator getVisibleBounds can not get bottom exactly on devices with virtual keys such as Galaxy Note 9

### Description
uiautomator getVisibleBounds can not get bottom exactly on devices with virtual keys such as Galaxy Note 9

### Steps to Reproduce
1.get a device with virtual key ,such as Galaxy Note 9 and hide virtual key
2.start an activity with textview in main layout, the id of main layout is "activity_main"
3.start uiautomator test
4.UiObject mainLayout getVisibleBounds()
5.get value of bottom

### Expected Results
the value of bottom is 2220
### Actual Results
the value of bottom is 2094
### AndroidX Test and Android OS Versions
com.android.support.test.uiautomator:uiautomator-v18:2.1.3
android 8.1.0
### Link to a public git repo demonstrating the problem:

Start by reproducing the Galaxy Note 9 case from the listed steps and inspect the UiObject.getVisibleBounds() entry point used for the activity_main layout. Compare the returned bottom value with the expected 2220 when virtual keys are hidden; done means the visible bounds report the correct bottom on devices with virtual keys without breaking other devices.

Written by the indexing model from the issue text.