Replace arrays with ArrayList

The three arrays were being reconstructed and copied for each add
and each remove. By replacing them with ArrayList only three
constructions total are required. Also, the number of
System.arraycopy() calls is halved.

Change-Id: I0f8def1b517eb1bc5f930fcd5d3d1e0394071f0e

Conflicts:
	core/java/android/view/WindowManagerGlobal.java