Add API docs for RemoteConnection VideoProvider/Callback.

Bug: 21573551
Change-Id: I434d83fa84f9515634776820b2e6a8004cf693ee
diff --git a/telecomm/java/android/telecom/Connection.java b/telecomm/java/android/telecom/Connection.java
index e2bbc62..c42e602 100644
--- a/telecomm/java/android/telecom/Connection.java
+++ b/telecomm/java/android/telecom/Connection.java
@@ -838,7 +838,8 @@
          * <p>
          * This could be in response to a preview request via
          * {@link #onRequestConnectionDataUsage()}, or as a periodic update by the
-         * {@link VideoProvider}.
+         * {@link VideoProvider}.  Where periodic updates of data usage are provided, they should be
+         * provided at most for every 1 MB of data transferred and no more than once every 10 sec.
          * <p>
          * Received by the {@link InCallService} via
          * {@link InCallService.VideoCall.Callback#onCallDataUsageChanged(long)}.