Remove unnecessary comment in metrics code

components/metrics/metrics_state_manager.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/metrics/metrics_state_manager.h"
 
 #include <stddef.h>
 
 #include "base/command_line.h"
 #include "base/guid.h"
@@ skipping 243 matching lines @@
       } else {
         client_id_with_dashes.push_back(*client_id_it);
         ++client_id_it;
       }
     }
     DCHECK(client_id_it == client_info->client_id.end());
     client_info->client_id.assign(client_id_with_dashes);
   }
 
   // The GUID retrieved (and possibly fixed above) should be valid unless
-  // retrieval failed.
-  // DCHECK(!client_info || base::IsValidGUID(client_info->client_id));
-  // Temporary hack for http://crbug.com/635255.
-  // TODO(asvitkine): address this the right way.
+  // retrieval failed. If not, return nullptr and generate a new GUID.

[Alexei Svitkine (slow), 2016/09/13 17:38:36]

"and generate a new GUID" part of the comment is confusing, because that's not
being done in this function.

I suggest expanding the comment to give more context, like ". This will result
in a new GUID being generated and backed up by the calling code FooBar()."

   if (client_info && !base::IsValidGUID(client_info->client_id))
     return nullptr;
 
   return client_info;
 }
 
 int MetricsStateManager::GetLowEntropySource() {
   UpdateLowEntropySource();
   return low_entropy_source_;
 }
@@ skipping 48 matching lines @@
 
   local_state_->ClearPref(prefs::kMetricsClientID);
   local_state_->ClearPref(prefs::kMetricsLowEntropySource);
   local_state_->ClearPref(prefs::kMetricsResetIds);
 
   // Also clear the backed up client info.
   store_client_info_.Run(ClientInfo());
 }
 
 }  // namespace metrics