Revert "Revert "Clear the bitmap associated with canvases.""

This reverts commit 4e012846cd09caa85b018c36810e9a64adb87640.
diff --git a/src/com/android/launcher2/HolographicOutlineHelper.java b/src/com/android/launcher2/HolographicOutlineHelper.java
index d2e1e7e..748d89e 100644
--- a/src/com/android/launcher2/HolographicOutlineHelper.java
+++ b/src/com/android/launcher2/HolographicOutlineHelper.java
@@ -199,6 +199,7 @@
                 mHolographicPaint);
 
         // cleanup
+        srcDstCanvas.setBitmap(null);
         brightOutline.recycle();
         thickOuterBlur.recycle();
         thickInnerBlur.recycle();