Performance/Frontend

Gavin:

• bug 853549 - Remove main-thread I/O from password manager
• bug 699854 - Refactor Downloads APIs to use async Storage
• bug 699850 - Refactor all synchronous history APIs to use async Storage APIs
• {{bug|876002)) - [meta] Remove nsIFormHistory2 so no synchronous form history code remains

Taras:

• bug 853388 + bug 853389 - JSON+Async addon manager