Do not add a single-pixel frame around the content pane when tabs are in use.

Other information:
I commonly run Epiphany maximized or fullscreen.  In either of these modes (with metacity as window manager), the scrollbar is at the right edge of the screen, and this is very convenient for Fitts' law reasons -- it's very easy to grab the scroll bar thumb by slamming the mouse into the side of the screen.

However, this only works when the Epiphany window contains only a single tab (i.e. no tabs are shown at the top, the content fills the whole pane below the toolbar).  When multiple tabs are displayed, then a thin border is added around the content pane, which doesn't really improve anything visually (if it were really critical aesthetically, presumably it would exist when no tabs were open as well), but does mean that the scroll bar thumb is no longer at the edge of the screen, and thus requires far more precise positioning to acquire with the mouse.  This is very frustrating.