Update browseable for MessagingService.

1. layout fixes
2. name changes in sample. (redo of ag/586904 which was lost from lmp-docs)

Change-Id: I3a2afafb5b878ba90b8ae6314220af19b3dfbb09

samples/browseable/MessagingService/src/com.example.android.messagingservice/Conversations.java

@@ -45,10 +45,10 @@ public class Conversations {
      * Senders of the said messages.
      */
     private static final String[] PARTICIPANTS = new String[]{
-            "John Rambo",
-            "Han Solo",
-            "Rocky Balboa",
-            "Lara Croft"
+            "John Smith",
+            "Robert Lawrence",
+            "James Smith",
+            "Jane Doe"
     };
 
     static class Conversation {