Revise the comment on base::IDMap::Replace()

IDMapOwnPointer mode was removed at https://codereview.chromium.org/2496653002,
but that mode is still mentioned in the comment on base::IDMap::Replace(). That
should be removed.

BUG=647091

Review-Url: https://codereview.chromium.org/2695393002
Cr-Commit-Position: refs/heads/master@{#451216}


CrOS-Libchrome-Original-Commit: 82e601f9fcd894f16fb9e4df96f71d7fc5af83f8
diff --git a/base/id_map.h b/base/id_map.h
index 8545de8..d171fb1 100644
--- a/base/id_map.h
+++ b/base/id_map.h
@@ -81,9 +81,8 @@
     }
   }
 
-  // Replaces the value for |id| with |new_data| and returns the existing value
-  // (as a unique_ptr<> if in IDMapOwnPointer mode).  Should only be called with
-  // an already added id.
+  // Replaces the value for |id| with |new_data| and returns the existing value.
+  // Should only be called with an already added id.
   V Replace(KeyType id, V new_data) {
     DCHECK(sequence_checker_.CalledOnValidSequence());
     DCHECK(!check_on_null_data_ || new_data);