add new column "real_date" for IM messages table.

Change-Id: I5c4b3da0843ff0205c2aff5f89639aba47a84e3b

core/java/android/provider/Im.java

@@ -896,11 +896,20 @@ public class Im {
         String BODY = "body";
 
         /**
-         * The date this message is sent or received
+         * The date this message is sent or received. This represents the display date for
+         * the message.
          * <P>Type: INTEGER</P>
          */
         String DATE = "date";
 
+        /**
+         * The real date for this message. While 'date' can be modified by the client
+         * to account for server time skew, the real_date is the original timestamp set
+         * by the server for incoming messages.
+         * <P>Type: INTEGER</P>
+         */
+        String REAL_DATE = "real_date";
+
         /**
          * Message Type, see {@link MessageType}
          * <P>Type: INTEGER</P>