content [nfc]: Use Divider instead of DecoratedBox.

[PIG208]

This should offer the same appearance for the spoiler divider despite being shorter.

Discovered while working on #823.

[PIG208]

Before	After

side by side

[chrisbobbe]

When I open the "Before" and "After" images in separate Chrome tabs, then switch between the tabs, I do see a difference in the appearance. I see more whitespace above the divider in the "After" image.

[PIG208]

Made a side-by-side version after zooming in on browser tabs:

[PIG208]

Oh I do find the difference visible when switching between tabs now. Let me investigate.

[PIG208]

Changed the height to 0. It should look identical to the old version now. An easy way to check in dev is through hot reloading with and without the commit.

Before	After

[chrisbobbe]

Sure, seems fine to me. Over to Greg for his review.

[gnprice]

I think this refactor isn't helpful. Divider is a Material widget — its main job is that it pulls in a bunch of defaults from Material Design.

This overrides three of the five defaults (color, height, thickness — the thickness defaults to 1 but is effectively forced to 0 by the zero height); for the other two, we want indent of zero not because that's the Material 3 default but because it's our design. We often use Material widgets for things like buttons and app navigation, but I think for the message content we generally have a pretty firm idea of what we want the design to look like and don't want it to depend on the choices in Material.

[PIG208]

Thanks for the explanation. Closing the PR.