On Flutter Web, platform views (like webview iframes) reside in their own DOM subtrees positioned above the WebGL canvas. As a result, they capture native browser pointer events and prevent them from bubbling up to the main document. When a user drags the widget inspector split pane resize bar, the drag interaction loses focus as soon as the cursor crosses the boundary and hovers over the webview iframe.

This results in significant jank and difficulty resizing the widget inspector pane.