SystemInfo Storage "watch" API Implementation

by Haojian Wu for Chromium

Chromium SystemInfo API is a set of web interfaces for Chrome Packaged App to query the hardware devices information and monitor the change events. The development of SystemInfo storage API is now in process. This project will implement new "watch" API for systemInfo.storage, including addWatch(), getAllWatch(), removeWatch(), removeAllWatch() functions. The new "watch" API will provide a more powful way for chrome packaged app to monitor storage devices change events.