In tiled mode, you can resize the full-screen video WebView to 1pt wide. This should not be possible.
<rdar://problem/20907914>
Created attachment 254753 [details] Patch
Related: <rdar://problem/21150721>
Committed r185473: <http://trac.webkit.org/changeset/185473>
Whaaa. This should not be using kWKLayoutModeDynamicSizeWithMinimumViewSize (nothing should! I just got here because I was about to delete it). Probably wanted the default, kWKLayoutModeViewSize. But also, you always reset to kWKLayoutModeViewSize, ignoring whatever it was before! I bet there's a lot of brokenness going into/out of fullscreen with a page that is scaled-down in Split View.
It's nontrivial to internally swap to a different layout mode and still come back to the right thing (respecting changes that come in from API clients, etc.), but I just implemented this for PDF, so we can probably reuse that.
Patch to move to the better thing: https://bugs.webkit.org/show_bug.cgi?id=148553