wmctrl says it's: 1024 x 767.
My laptop is docked, driving a display at 1680 x 1050 via hdmi, and its normal screen (1366 x 768), is turned off.
00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09) (prog-if 00 [VGA controller])
Subsystem: Lenovo Device 21da
Flags: bus master, fast devsel, latency 0, IRQ 51
Memory at f0000000 (64-bit, non-prefetchable) [size=4M]
Memory at e0000000 (64-bit, prefetchable) [size=256M]
I/O ports at 5000 [size=64]
Expansion ROM at <unassigned> [disabled]
Capabilities: <access denied>
Kernel driver in use: i915
Kernel modules: i915
Window Manager must be Unity/Gnome/ Compiz, or whatever is standard on Ubuntu 12.04.