Fix missing super call in PreviewPlacerView.onDetachedFromWindow

Change-Id: Iea79c0081cb66f54f161c0cf02cb365fcf88a07c
diff --git a/java/src/com/android/inputmethod/keyboard/internal/PreviewPlacerView.java b/java/src/com/android/inputmethod/keyboard/internal/PreviewPlacerView.java
index 4b0d4fb..83a06cb 100644
--- a/java/src/com/android/inputmethod/keyboard/internal/PreviewPlacerView.java
+++ b/java/src/com/android/inputmethod/keyboard/internal/PreviewPlacerView.java
@@ -173,6 +173,7 @@
 
     @Override
     protected void onDetachedFromWindow() {
+        super.onDetachedFromWindow();
         mGestureFloatingPreviewText.onDetachFromWindow();
         freeOffscreenBuffer();
     }