Auto enable/disable pie when expanded desktop mode state changed.

Change-Id: Id6757a30cb7ada4b662d8b482be404ab95c9d018

	修改：      core/java/android/provider/Settings.java
	修改：      policy/src/com/android/internal/policy/impl/GlobalActions.java
Merge "Auto enable/disable pie when expanded desktop mode state changed." into jb-mr2_mkt