This fixes a number of things that are warnings in the Mac compiler....

statsreport/uploader_aggregation-mac.mm

 /*
  * Copyright 2009, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 94 matching lines @@
       case 'L': // "LastTransmission"
         break;
     }
     if (current != NULL)
       formatter.AddMetric(current);
   }
 
   DLOG(INFO) << "formatter.output() = " << formatter.output();
   return stats_uploader->UploadMetrics(extra_url_data,
                                        user_agent,
-                                       formatter.output());
+                                       formatter.output().c_str());
 }
 
 void ResetPersistentMetrics() {
   NSError *error = nil;
   /*
   [[NSFileManager defaultManager] removeItemAtPath:O3DStatsPath()
                                              error:&error];
                                              */
   [[NSFileManager defaultManager] removeFileAtPath:O3DStatsPath()
                                            handler:nil];
@@ skipping 110 matching lines @@
 
 // Used primarily for testing. Default functionality.
 bool StatsUploader::UploadMetrics(const char* extra_url_data,
                                   const char* user_agent,
                                   const char *content) {
   return stats_report::UploadMetrics(extra_url_data, user_agent, content);
 }
 
 
 }  // namespace stats_report