Refactor TestingPrefStore to make it useful to some tests of load errors and asynchrony.

base/prefs/pref_store_observer_mock.cc

Index: base/prefs/pref_store_observer_mock.cc
diff --git a/base/prefs/pref_store_observer_mock.cc b/base/prefs/pref_store_observer_mock.cc
index 0970e6310d776f29fe40dba381f5c20eb107b54d..f1a31bb985d2032ce2fc056e975923a899a255a3 100644
--- a/base/prefs/pref_store_observer_mock.cc
+++ b/base/prefs/pref_store_observer_mock.cc
@@ -4,6 +4,26 @@
 
 #include "base/prefs/pref_store_observer_mock.h"
 
-PrefStoreObserverMock::PrefStoreObserverMock() {}
+#include "testing/gtest/include/gtest/gtest.h"
+
+PrefStoreObserverMock::PrefStoreObserverMock()
+    : initialized(false), initialization_success(false) {}
 
 PrefStoreObserverMock::~PrefStoreObserverMock() {}
+
+void PrefStoreObserverMock::VerifyAndResetChangedKey(
+    const std::string& expected) {
+  EXPECT_EQ(1u, changed_keys.size());
+  if (changed_keys.size() >= 1)
+    EXPECT_EQ(expected, changed_keys.front());
+  changed_keys.clear();
+}
+
+void PrefStoreObserverMock::OnPrefValueChanged(const std::string& key) {
+  changed_keys.push_back(key);
+}
+
+void PrefStoreObserverMock::OnInitializationCompleted(bool success) {
+  initialized = true;
+  initialization_success = success;
+}