Zoom Options Dialog (Universal Access)
GNOME Shell has a built-in magnification feature whose configuration relies on GSettings for (1) preferences persistence and (2) reacting to changes to settings. The only configuration for this is currently an on/off switch that is provided in the shell universal access menu and in the control-center panel. The goal of this feature is to provide access to a reasonable subset of magnifier configuration options from the control-center panel. Further details are given on the GNOME Shell Magnifier page.
gnome-control-center (patch review), a11y team
As of January 21 (or so), the zoom options dialog has been merged into gnome-control-center.
This feature was planned for GNOME 3.2, but it was not discussed or proposed formally for that release and did not have an owner until late in the 3.2 cycle.
Several versions of the UI have been submitted and discussed with the design team and progressively modified. A screen shot of the latest is shown above. This is the one that was merged.
This feature is tracked in bugzilla: