I've got an issue with the WebBrowserComponent on 10.11, which isn't a problem on 10.9. It seems that it steals mouse focus as soon as the mouse enters the component (even if dragging on another component). This means that when I am trying to resize it using StretchableLayout components, I can't make the WebBrowserComponent's area smaller, without going exteremly slowly and staying over the StretchableLayoutResizerBar.
hopefully this video makes the issue a little clearer:
https://dl.dropboxusercontent.com/u/33721778/WebBrowserComponentProblem.mov