WebView doesn't get resized or panned when soft keyboard is overlayed

I'm using Xamarin Forms 2.3.3.175, the latest version, and testing on Lollipop emulator.

When the input field in a WebView get focused, the software keyboard is scrolling up and the input field is overlayed.
The keyboard hides the focused input field as shown in the screenshots.

If I create and click a Entry rather than the WebView, it resizes the content page as expected.
I've searched a lot with this issue but none of them works with WebView case.(including setting WindowSoftInputMode = SoftInput.AdjustResize on Activity)

I can say this behavior in Xamarin.Forms is buggy because If I create a WebView in Android with Activity rather than FormsAppCompatActivity, the WebView is scrolled up OK.

My test codes are just a simple WebView in a ScrollView