Create a PrefStore in support of Blimp metrics collection.

components/prefs/in_memory_pref_store.cc

Index: components/prefs/in_memory_pref_store.cc
diff --git a/components/prefs/in_memory_pref_store.cc b/components/prefs/in_memory_pref_store.cc
new file mode 100644
index 0000000000000000000000000000000000000000..c222a3680ac232aeb2ee1bdf6c43a8d953b290e7
--- /dev/null
+++ b/components/prefs/in_memory_pref_store.cc
@@ -0,0 +1,76 @@
+// Copyright (c) 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 "components/prefs/in_memory_pref_store.h"
+
+#include <memory>
+#include <utility>
+
+#include "base/values.h"
+
+InMemoryPrefStore::InMemoryPrefStore() {}
+
+InMemoryPrefStore::~InMemoryPrefStore() {}
+
+bool InMemoryPrefStore::GetValue(const std::string& key,
+                                 const base::Value** value) const {
+  return prefs_.GetValue(key, value);
+}
+
+bool InMemoryPrefStore::GetMutableValue(const std::string& key,
+                                        base::Value** value) {
+  return prefs_.GetValue(key, value);
+}
+
+void InMemoryPrefStore::AddObserver(PrefStore::Observer* observer) {
+  observers_.AddObserver(observer);
+}
+
+void InMemoryPrefStore::RemoveObserver(PrefStore::Observer* observer) {
+  observers_.RemoveObserver(observer);
+}
+
+bool InMemoryPrefStore::HasObservers() const {
+  return observers_.might_have_observers();
+}
+
+bool InMemoryPrefStore::IsInitializationComplete() const {
+  return true;
+}
+
+void InMemoryPrefStore::SetValue(const std::string& key,
+                                 std::unique_ptr<base::Value> value,
+                                 uint32_t flags) {
+  DCHECK(value);
+  if (prefs_.SetValue(key, std::move(value)))
+    ReportValueChanged(key, flags);
+}
+
+void InMemoryPrefStore::SetValueSilently(const std::string& key,
+                                      std::unique_ptr<base::Value> value,
+                                      uint32_t flags) {
+  prefs_.SetValue(key, std::move(value));
+}
+
+void InMemoryPrefStore::RemoveValue(const std::string& key, uint32_t flags) {
+  if (prefs_.RemoveValue(key))
+    ReportValueChanged(key, flags);
+}
+
+bool InMemoryPrefStore::ReadOnly() const {
+  return false;
+}
+
+PersistentPrefStore::PrefReadError InMemoryPrefStore::GetReadError() const {
+  return PersistentPrefStore::PREF_READ_ERROR_NONE;
+}
+
+PersistentPrefStore::PrefReadError InMemoryPrefStore::ReadPrefs() {
+  return PersistentPrefStore::PREF_READ_ERROR_NONE;
+}
+
+void InMemoryPrefStore::ReportValueChanged(const std::string& key,
+                                           uint32_t flags) {
+  FOR_EACH_OBSERVER(Observer, observers_, OnPrefValueChanged(key));
+}