Remove the last usages of PrefObserver outside of Prefs.

chrome/browser/prefs/pref_observer_mock.cc

Index: chrome/browser/prefs/pref_observer_mock.cc
diff --git a/chrome/browser/prefs/pref_observer_mock.cc b/chrome/browser/prefs/pref_observer_mock.cc
deleted file mode 100644
index 0b3f82ad7dbed15771e9c50361ccdcb1f466086e..0000000000000000000000000000000000000000
--- a/chrome/browser/prefs/pref_observer_mock.cc
+++ /dev/null
@@ -1,17 +0,0 @@
-// Copyright (c) 2011 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/prefs/pref_observer_mock.h"
-#include "chrome/common/chrome_notification_types.h"
-
-PrefObserverMock::PrefObserverMock() {}
-
-PrefObserverMock::~PrefObserverMock() {}
-
-void PrefObserverMock::Expect(PrefServiceBase* prefs,
-                              const std::string& pref_name,
-                              const Value* value) {
-  EXPECT_CALL(*this, OnPreferenceChanged(prefs, pref_name))
-      .With(PrefValueMatches(prefs, pref_name, value));
-}