Add a PersistentStore to FeatureEngagementTracker

components/feature_engagement_tracker/internal/test/event_util.cc

+// Copyright 2017 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/feature_engagement_tracker/internal/test/event_util.h"
+
+#include <map>

[nyquist, 2017/05/11 17:08:03]

Nit: Did you end up using this include? Maybe I'm just not seeing it.

[David Trainor- moved to gerrit, 2017/05/11 19:30:28]

Done.

+
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace feature_engagement_tracker {
+namespace test {
+
+void SetEventCountForDay(Event* event, uint32_t day, uint32_t count) {
+  Event_Count* event_count = event->add_events();
+  event_count->set_day(day);
+  event_count->set_count(count);
+}
+
+void VerifyEventCount(const Event* event, uint32_t day, uint32_t count) {
+  bool found_day = false;
+  for (int i = 0; i < event->events_size(); ++i) {

[nyquist, 2017/05/11 17:08:03]

Nit: I know you just moved this around, but should we consider using:
for (const auto& event_count : event->events()) {
  ...

here and below? I don't feel strongly though.
It seems like it's a thing:
https://developers.google.com/protocol-buffers/docs/reference/cpp-generated#r...
const RepeatedPtrField<Bar>& foo() const;

[David Trainor- moved to gerrit, 2017/05/11 19:30:28]

Done.

+    Event_Count event_count = event->events(i);
+    if (event_count.day() == day) {
+      EXPECT_FALSE(found_day);
+      found_day = true;
+      EXPECT_EQ(count, event_count.count());
+    }
+  }
+  EXPECT_TRUE(found_day);
+}
+
+void VerifyEventsEqual(const Event* a, const Event* b) {
+  if (!a || !b) {
+    // If one of the events are nullptr, both should be nullptr.
+    ASSERT_EQ(a, b);
+    return;
+  }
+
+  EXPECT_EQ(a->name(), b->name());
+  EXPECT_EQ(a->events_size(), b->events_size());
+  for (int i = 0; i < a->events_size(); ++i) {
+    VerifyEventCount(b, a->events(i).day(), a->events(i).count());
+  }
+}
+
+}  // namespace test
+}  // namespace feature_engagement_tracker