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/BubbleTextView.java

@@ -45,7 +45,7 @@ public class BubbleTextView extends TextView {
 
     private int mPrevAlpha = -1;
 
-    private final HolographicOutlineHelper mOutlineHelper = new HolographicOutlineHelper();
+    private final HolographicOutlineHelper mOutlineHelper = HolographicOutlineHelper.obtain();
     private final Canvas mTempCanvas = new Canvas();
     private final Rect mTempRect = new Rect();
     private boolean mDidInvalidateForPressedState;