An official image of Google’s Nexus 7 tablet has been pulled from the Google Play store and published online. The Asus-built slate is expected to be unveiled during Google’s keynote at its annual I/O Developer Conference in San Francisco on Wednesday. The device is rumored to feature a quad-core Tegra 3 processor clocked at 1.3GHz, a GeForce 12-core GPU, 1GB of RAM and Google’s latest Android operating system — Android 4.1 Jelly Bean.