Move active field trial API to variations component.

components/variations/active_field_trials.cc

Index: components/variations/active_field_trials.cc
===================================================================
--- components/variations/active_field_trials.cc	(revision 0)
+++ components/variations/active_field_trials.cc	(working copy)
@@ -0,0 +1,76 @@
+// 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/variations/active_field_trials.h"
+
+#include <vector>
+
+#include "base/strings/stringprintf.h"
+#include "base/strings/utf_string_conversions.h"
+#include "components/variations/metrics_util.h"
+
+namespace chrome_variations {
+
+namespace {
+
+// Populates |name_group_ids| based on |active_groups|.
+void GetFieldTrialActiveGroupIdsForActiveGroups(
+    const base::FieldTrial::ActiveGroups& active_groups,
+    std::vector<ActiveGroupId>* name_group_ids) {
+  DCHECK(name_group_ids->empty());
+  for (base::FieldTrial::ActiveGroups::const_iterator it =
+       active_groups.begin(); it != active_groups.end(); ++it) {
+    name_group_ids->push_back(MakeActiveGroupId(it->trial_name,
+                                                it->group_name));
+  }
+}
+
+}  // namespace
+
+ActiveGroupId MakeActiveGroupId(const std::string& trial_name,
+                                const std::string& group_name) {
+  ActiveGroupId id;
+  id.name = metrics::HashName(trial_name);
+  id.group = metrics::HashName(group_name);
+  return id;
+}
+
+void GetFieldTrialActiveGroupIds(
+    std::vector<ActiveGroupId>* name_group_ids) {
+  DCHECK(name_group_ids->empty());
+  // A note on thread safety: Since GetActiveFieldTrialGroups() is thread
+  // safe, and we operate on a separate list of that data, this function is
+  // technically thread safe as well, with respect to the FieldTrialList data.
+  base::FieldTrial::ActiveGroups active_groups;
+  base::FieldTrialList::GetActiveFieldTrialGroups(&active_groups);
+  GetFieldTrialActiveGroupIdsForActiveGroups(active_groups,
+                                             name_group_ids);
+}
+
+void GetFieldTrialActiveGroupIdsAsStrings(
+    std::vector<std::string>* output) {

[Ilya Sherman, 2014/05/19 12:29:42]

nit: I think this fits on the previous line.  Might be worth running "git cl
format".

[Alexei Svitkine (slow), 2014/05/19 12:50:47]

Done.

+  DCHECK(output->empty());
+  std::vector<ActiveGroupId> name_group_ids;
+  GetFieldTrialActiveGroupIds(&name_group_ids);
+  for (size_t i = 0; i < name_group_ids.size(); ++i) {
+    output->push_back(base::StringPrintf(
+        "%x-%x", name_group_ids[i].name, name_group_ids[i].group));
+  }
+}
+
+// Functions below are exposed for testing explicitly behind this namespace.
+// They simply wrap existing functions in this file.

[Ilya Sherman, 2014/05/19 12:29:42]

nit: Probably not necessary to duplicate this comment from the header file.

[Alexei Svitkine (slow), 2014/05/19 12:50:47]

Done.

+namespace testing {
+
+void TestGetFieldTrialActiveGroupIds(
+    const base::FieldTrial::ActiveGroups& active_groups,
+    std::vector<ActiveGroupId>* name_group_ids) {
+  GetFieldTrialActiveGroupIdsForActiveGroups(active_groups,
+                                             name_group_ids);
+}
+
+}  // namespace testing
+
+
+}  // namespace chrome_variations