Support add-on 'field trial' records.

components/variations/active_field_trials.h

 // 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.
 
 #ifndef COMPONENTS_VARIATIONS_ACTIVE_FIELD_TRIALS_H_
 #define COMPONENTS_VARIATIONS_ACTIVE_FIELD_TRIALS_H_
 
 #include <stdint.h>
 
 #include <string>
 
 #include "base/metrics/field_trial.h"
+#include "base/strings/string_piece.h"
 
 namespace variations {
 
 // The Unique ID of a trial and its active group, where the name and group
 // identifiers are hashes of the trial and group name strings.
 struct ActiveGroupId {
   uint32_t name;
   uint32_t group;
 };
 
 // Returns an ActiveGroupId struct for the given trial and group names.
-ActiveGroupId MakeActiveGroupId(const std::string& trial_name,
-                                const std::string& group_name);
+ActiveGroupId MakeActiveGroupId(base::StringPiece trial_name,
+                                base::StringPiece group_name);
 
 // We need to supply a Compare class for templates since ActiveGroupId is a
 // user-defined type.
 struct ActiveGroupIdCompare {
   bool operator() (const ActiveGroupId& lhs, const ActiveGroupId& rhs) const {
     // The group and name fields are just SHA-1 Hashes, so we just need to treat
     // them as IDs and do a less-than comparison. We test group first, since
     // name is more likely to collide.
     if (lhs.group != rhs.group)
       return lhs.group < rhs.group;
@@ skipping 27 matching lines @@
 
 void TestGetFieldTrialActiveGroupIds(
     const base::FieldTrial::ActiveGroups& active_groups,
     std::vector<ActiveGroupId>* name_group_ids);
 
 }  // namespace testing
 
 }  // namespace variations
 
 #endif  // COMPONENTS_VARIATIONS_ACTIVE_FIELD_TRIALS_H_