Convert FieldTrialActivated to use mojo.

chrome/browser/field_trial_recorder.cc

+// Copyright 2016 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 "chrome/browser/field_trial_recorder.h"
+
+#include "base/metrics/field_trial.h"
+#include "mojo/public/cpp/bindings/strong_binding.h"
+
+FieldTrialRecorder::FieldTrialRecorder() = default;
+
+FieldTrialRecorder::~FieldTrialRecorder() = default;
+
+// static
+void FieldTrialRecorder::Create(
+    chrome::mojom::FieldTrialRecorderRequest request) {
+  mojo::MakeStrongBinding(base::MakeUnique<FieldTrialRecorder>(),
+                          std::move(request));
+}
+
+void FieldTrialRecorder::FieldTrialActivated(const std::string& trial_name) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  // Activate the trial in the browser process to match its state in the
+  // renderer. This is done by calling FindFullName which finalizes the group
+  // and activates the trial.
+  base::FieldTrialList::FindFullName(trial_name);
+}