Avoid rerendering EventTiles when not necessary

[richvdh]

Each individual eventtile isn't particularly expensive, but when you have 500
of them, they start adding up. Shuffle some of the stuff into MessagePanel, so
that we can shouldComponentUpdate EventTiles properly.

[ara4n]

lgtm, although i'm a bit surprised this is needed and is easier than fixing whatever has increased the timeline-rerendering regression in the first place?

[ara4n]

hm, is this going to handle the redraw required when a LinkPreviewWidget finishes loading ok?

[richvdh]

hm, is this going to handle the redraw required when a LinkPreviewWidget finishes loading ok?

what redraw? The LinkPreviewWidget itself will need a re-render, but it handles that itself. There is no need for EventTile to re-render at this stage.