touch: Change how touch-screen capability is processed.

ui/events/devices/touchscreen_device.h

Index: ui/events/devices/touchscreen_device.h
diff --git a/ui/events/devices/touchscreen_device.h b/ui/events/devices/touchscreen_device.h
index 2f11cec55e5afbd29a9b2f6aaf5aff7704225e00..d7b1fc4a32ab6415bb755f8a7e971acfcf5bf7de 100644
--- a/ui/events/devices/touchscreen_device.h
+++ b/ui/events/devices/touchscreen_device.h
@@ -21,10 +21,12 @@ struct EVENTS_DEVICES_EXPORT TouchscreenDevice : public InputDevice {
   TouchscreenDevice(unsigned int id,
                     InputDeviceType type,
                     const std::string& name,
-                    const gfx::Size& size);
+                    const gfx::Size& size,
+                    int touch_points);
 
-  // Size of the touch screen area.
-  gfx::Size size;
+  gfx::Size size;    // Size of the touch screen area.
+  int touch_points;  // The number of touch points this device supports (0 if
+                     // unknown).
 };
 
 }  // namespace ui