Split testing_pref_service.h/.cc into two parts, generic vs. Chrome-specific.

chrome/test/base/scoped_testing_local_state.cc

+// Copyright (c) 2013 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/test/base/scoped_testing_local_state.h"
+
+#include "chrome/browser/prefs/browser_prefs.h"
+#include "chrome/test/base/testing_browser_process.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+ScopedTestingLocalState::ScopedTestingLocalState(
+    TestingBrowserProcess* browser_process)
+    : browser_process_(browser_process) {
+  chrome::RegisterLocalState(&local_state_, local_state_.registry());
+  EXPECT_FALSE(browser_process->local_state());
+  browser_process->SetLocalState(&local_state_);
+}
+
+ScopedTestingLocalState::~ScopedTestingLocalState() {
+  EXPECT_EQ(&local_state_, browser_process_->local_state());
+  browser_process_->SetLocalState(NULL);
+}