Issue here is that the timer ticks and sets the tool tip text even when the mouse is out of the webview. I've been able to reproduce this when a toolbar is at the top of the webview and you move your mouse out through the top.
I have a simple fix in place but there could possibly be something cleaner. Right now I just added a boolean for "hasMouseInside" and set it to false on mouse leave, and true on mouse enter. Then just check the boolean before we display the tool tip.