Android-specific meta-viewport property. "If it is not specified, it uses the default, 160dpi as of today. Then the 1.0 scale factor specified in the viewport tag means 100% on G1 and 150% on Sholes. If you set 'target-densityDpi' to 'device-dpi', then the 1.0 scale factor means 100% on both G1 and Sholes."