Fixing preview for newly created folder not getting clipped properly.

When a new folder was created, isClipping was set to false so that the stroke is
drawn behind the previewItems, but it was never reset to true.

Bug: 37654209
Change-Id: I03e94008dd19d8c5a0acb61207ebac33860fdf1d
diff --git a/src/com/android/launcher3/folder/PreviewBackground.java b/src/com/android/launcher3/folder/PreviewBackground.java
index eb6a6d5..61490ee 100644
--- a/src/com/android/launcher3/folder/PreviewBackground.java
+++ b/src/com/android/launcher3/folder/PreviewBackground.java
@@ -306,6 +306,7 @@
     // It is the callers responsibility to save and restore the canvas layers.
     void clipCanvasHardware(Canvas canvas) {
         mPaint.setColor(Color.BLACK);
+        mPaint.setStyle(Paint.Style.FILL);
         mPaint.setXfermode(mClipPorterDuffXfermode);
 
         float radius = getScaledRadius();
@@ -336,6 +337,7 @@
         }
 
         mDrawingDelegate = null;
+        isClipping = true;
         invalidate();
     }