Make HolographicOutlineHelper a singleton.

It's a pretty heavy object, including three Paints at 74
bytes apiece, and we allocate one for every workspace and
every icon. We really only need one.

Change-Id: Ic9e12d478c3be27b13133718875c91540f7ccf4c

src/com/android/launcher3/Workspace.java

@@ -167,7 +167,7 @@ public class Workspace extends SmoothPagedView
     /** Is the user is dragging an item near the edge of a page? */
     private boolean mInScrollArea = false;
 
-    private final HolographicOutlineHelper mOutlineHelper = new HolographicOutlineHelper();
+    private final HolographicOutlineHelper mOutlineHelper = HolographicOutlineHelper.obtain();
     private Bitmap mDragOutline = null;
     private final Rect mTempRect = new Rect();
     private final int[] mTempXY = new int[2];