Fix app to folder icon animation.

- Needed to account for the preview bounds (similar to BubbleTextView icon
  bounds)
- Also needed to update the bitmap shift amount so that it is re-centered
- Moved ShiftedBitmapDrawable to its own class in graphics package

Bug: 123900446
Change-Id: Ifa9e3f688e55d017cf86a0285f5cdb1b014f01e6

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

@@ -189,6 +189,10 @@ public class FolderIcon extends FrameLayout implements FolderListener {
         return icon;
     }
 
+    public void getPreviewBounds(Rect outBounds) {
+        mBackground.getBounds(outBounds);
+    }
+
     public Folder getFolder() {
         return mFolder;
     }