Setting the callback for previewItems to folderIcon. This allows the FolderIcon to get updated

without going through the child'draw pass.
Also simplifying the draw code for the FolderIcon to remove any cycling invalidate calls

Bug: 62900800
Change-Id: I17009a5347a1c3c35426313ac759e0240ce6a395

src/com/android/launcher3/folder/StackFolderIconLayoutRule.java

@@ -35,7 +35,7 @@ public class StackFolderIconLayoutRule implements FolderIcon.PreviewLayoutRule {
     private float mMaxPerspectiveShift;
 
     @Override
-    public void init(int availableSpace, int intrinsicIconSize, boolean rtl) {
+    public void init(int availableSpace, float intrinsicIconSize, boolean rtl) {
         mAvailableSpaceInPreview = availableSpace;
 
         // cos(45) = 0.707  + ~= 0.1) = 0.8f