Revert "Clear the bitmap associated with canvases."

This reverts commit 9b9d48f289.

src/com/android/launcher2/IconCache.java

@@ -101,7 +101,6 @@ public class IconCache {
         Canvas c = new Canvas(b);
         d.setBounds(0, 0, b.getWidth(), b.getHeight());
         d.draw(c);
-        c.setBitmap(null);
         return b;
     }