Added Talkback announcements for Data Saver switch.

BUG: 27504554
Change-Id: I6a6b996fe03a565edc051cf24a8ec7de4e8e5644
diff --git a/packages/SystemUI/src/com/android/systemui/qs/tiles/DataSaverTile.java b/packages/SystemUI/src/com/android/systemui/qs/tiles/DataSaverTile.java
index fa235d3..74b3fdc 100644
--- a/packages/SystemUI/src/com/android/systemui/qs/tiles/DataSaverTile.java
+++ b/packages/SystemUI/src/com/android/systemui/qs/tiles/DataSaverTile.java
@@ -73,6 +73,15 @@
     }
 
     @Override
+    protected String composeChangeAnnouncement() {
+        if (mState.value) {
+            return mContext.getString(R.string.accessibility_quick_settings_data_saver_changed_on);
+        } else {
+            return mContext.getString(R.string.accessibility_quick_settings_data_saver_changed_off);
+        }
+    }
+
+    @Override
     public void onDataSaverChanged(boolean isDataSaving) {
         refreshState(isDataSaving);
     }