Add documentation about clearing usage stats

Bug 5475575

Change-Id: Idee771a6b29dcd4870090cd1b5c72e126886fb47

Author: Makoto Onuki

core/java/android/provider/ContactsContract.java

@@ -7452,7 +7452,7 @@ private ProviderStatus() {
     /**
      * <p>
      * API allowing applications to send usage information for each {@link Data} row to the
-     * Contacts Provider.
+     * Contacts Provider.  Applications can also clear all usage information.
      * </p>
      * <p>
      * With the feedback, Contacts Provider may return more contextually appropriate results for
@@ -7497,6 +7497,12 @@ private ProviderStatus() {
      * boolean successful = resolver.update(uri, new ContentValues(), null, null) > 0;
      * </pre>
      * </p>
+     * <p>
+     * Applications can also clear all usage information with:
+     * <pre>
+     * boolean successful = resolver.delete(DataUsageFeedback.FEEDBACK_URI, null, null) > 0;
+     * </pre>
+     * </p>
      */
     public static final class DataUsageFeedback {