Emulator

What's the problem? Describe what went wrong.

When saving a state, a blank OSD message box usually appears and disappears before showing the successful save OSD message. It appears when the "Saving State..." OSD message is expected but the message box is much larger than that. Easier to reproduce by saving the state multiple times. Code in OSD::DrawMessages's for loop is initially triggered once as expected, but eventually becomes triggered multiple times per each OSD message.

First noticed in https://dolphin-emu.org/download/dev/b1fecbb71ce256d7c70963414a30501570c2e871/ but may not be a regression.

Is there anything else that can help developers narrow down the issue? (e.g. logs, screenshots,
configuration files, savefiles, savestates)

Copied over from https://github.com/dolphin-emu/dolphin/pull/9004#pullrequestreview-468819128 so we don't forget about it.