Frame is missing elevation and shadow inside ListView

Description

Frame shadow and elevation looks different when upgrade from 3.2 to 3.3 or 3.4 pre when used inside ListView. It looks more flat and very similar to #3532. Tested the issue on Android emulator 8.0 and also on device HTC U11 with Android 8.0

Steps to Reproduce

1. Create Xamarin.Forms project (Blank, .NET Standard, Android)
2. Use Xaml: <StackLayout Orientation="Vertical"> <Frame Padding="1" HasShadow="True"> <Label Text="Test" /> </Frame> <Frame Padding="1" HasShadow="True"> <Label Text="Test" /> </Frame> <ListView HasUnevenRows="True" ItemsSource="{Binding ListItems}" SeparatorVisibility="None"> <ListView.ItemTemplate> <DataTemplate> <ViewCell> <Grid Margin="5"> <Grid.RowDefinitions> <RowDefinition Height="50" /> </Grid.RowDefinitions> <Frame Padding="1" HasShadow="True"> <Label Text="{Binding}" /> </Frame> </Grid> </ViewCell> </DataTemplate> </ListView.ItemTemplate> </ListView> </StackLayout>

Expected Behavior

Frame has visible shadow and elevation

Actual Behavior

Frame looks flat and does not have a shadow when placed inside ListView

Basic Information

• Version with issue: 3.3.0.967583, 3.3.0.967583, both of the 3.4 pre versions
• Last known good version: 3.2.0.871581
• IDE: Visual Studio Enterprise 2017 15.8.9
• Platform Target Frameworks:
  • Android: 8.0
• Nuget Packages: default

Screenshots

All fine on 3.2

Elevation and shadow missing inside ListView on 3.3+