Add API for applications to handle memory pressure
@hadess
Submitted by Bastien Nocera Link to original bug (#741300)
Description
CGroups offer the ability to setup a level of memory pressure at which the application would get told that memory is scarce, so it can start taking steps to reduce its own memory consumption.
For example, dropping memory caches, stopping unused background tasks (tabs in a web browser), etc.
This is the iOS API to get us started: https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIApplicationDelegate_Protocol/index.html#//apple_ref/occ/intfm/UIApplicationDelegate/applicationDidReceiveMemoryWarning: