Contacts headers now update properly when you fast scroll backwards slowly.

video: https://drive.google.com/open?id=0B2Hce9qilHmvdl8xY1hmcDZ0R3M
Test: manual
PiperOrigin-RevId: 161713747
Change-Id: I8185ca897a82479ef7c552a1ce6891e31c4c5aad
diff --git a/java/com/android/dialer/contactsfragment/FastScroller.java b/java/com/android/dialer/contactsfragment/FastScroller.java
index 0223c5f..2a86a3b 100644
--- a/java/com/android/dialer/contactsfragment/FastScroller.java
+++ b/java/com/android/dialer/contactsfragment/FastScroller.java
@@ -91,6 +91,7 @@
     int targetPos = getValueInRange(0, itemCount - 1, (int) scrolledPosition);
     layoutManager.scrollToPositionWithOffset(targetPos, 0);
     container.setText(adapter.getHeaderString(targetPos));
+    adapter.refreshHeaders();
   }
 
   // Returns a float in range [0, 1] which represents the position of the scroller.