It will help reduce memory footprint of Launcher, when in background.
It is required to help deallocate images, when Google Now Launcher
goes into the background. See cl/83222937/ .
Change-Id: I6d3d4d1f0457c67abcad3ba4516c87abcf666b05
-> When extending the Launcher Activity, instead of overriding
public and protected methods, create a proper interface
-> This helps define the interface when extending Launcher
more formally and more clearly
Change-Id: Ib38e8a376b2242d4078bf6856bb145f5b5f0da80