That window geometry info was usually provided by the window manager. Some apps still do it on their own, notably some terminal apps that report the width and height in characters during a resize -- which is far more useful than reporting in pixels for that kind of program.
xfce4-terminal does this.
I don't know how well the following commands will play with Gnome 3, and I don't have Gnome 3 handy to try them, but they might work.
In a traditional X environment you can use
xev -id <window> to monitor X events on the specified window. Those events include
ConfigureNotify events that report, among other things, the window's position, width, and height. To show only the interesting geometry-changing events use
xev -id <window> -event structure. You'll have to use something like
xwininfo to discover the window ID to give to
To resize and/or move a window from the command line, use
-e option to
wmctrl takes an optarg of the form
<gravity>,<posx>,<posy>,<width>,<height> with certain values reserved to mean "do not change". To change a window's width and height while keeping its gravity and position unchanged specify
0,-1,-1,<width>,<height>. The easiest way to choose the target window for
wmctrl is to use the
-r :SELECT: option, but if you happen to know the window ID in advance then you can give that to
-r, typically with an additional flag like
-i to specify that the ID should be understood as a numeric ID.
man xev and
man wmctrl have all the gory details.