This month, Google launched Chrome DevTools for mobile.
Web apps are expected to render perfectly on mobile and look good on multiple screens. The new Chrome DevTools for Mobile allows developers to go through the popular device screens without having to leave the development environment. All you have to do is select a device from the Emulation tab and all relevant viewport properties will be set.
Chrome Beta (including ChromeOS) now supports native USB discovery for connected devices, with no necessary configuration and an entirely optional adb cimmand line. While connected via USB, you can screencast the full viewport from the device directly to Chrome DevTools and keyboard/mouse events are sent from DevTools to your device.