Click inside the first text area, select all, delete.
Safari sends you back to the previous page instead of deleting the contents of the text area.
We select iframes and other special elements when their contents are fully selected, to make them easier to delete when they occur in an editable region. I think that's what's happening here. Since the special element itself isn't editable, the delete key is responded to with a Back instead of a delete operation.
Created attachment 6799 [details]
In selectFrameElementInParentIfFullySelected, we should only select the frame in its parent if the frame is in an editable region.
Also, WebCore wasn't treating mouse events that the eventSender was sending as distinct events, since they all had the same eventNumber (0). This was sending us into different code paths than we get into when a user does mouse clicks. So, I added an eventNumber to the eventSender and increment it every time DRT creates an event.
Created attachment 6801 [details]