Remember Tyler Hall’s personal story About the UX moment where there was no visible indication in the iOS pop-up context menu that the content inside was scrollable? The thing his mom wanted to do seemed impossible, iOS isn’t alone here – Documents by Terence Eden basically the same problem on Android:
I tried to share a website with the Android version of Google Chrome. I clicked the split button and a panel appeared at the bottom of the screen.
Hmmm, it didn’t have the number of shares you wanted. It was early in the morning – when I’m not at my best cognitively – and I was stunned. There is nothing on this screen other than icons that tell me how I can interact with it. No scroll bar, no handle, no “add” icon, nothing.
I would guess even fairly subtle “scroll shadows” would go a long way in both cases, but serious user testing should be fine here.