Reduce unneeded policy fetches by detecting expired invalidations.

chrome/browser/policy/cloud/cloud_policy_browsertest.cc

 // Copyright (c) 2012 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 "base/callback.h"
 #include "base/command_line.h"
 #include "base/file_util.h"
 #include "base/files/file_path.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/path_service.h"
 #include "base/prefs/pref_service.h"
 #include "base/run_loop.h"
 #include "base/strings/stringprintf.h"
+#include "base/time/time.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/invalidation/fake_invalidation_service.h"
 #include "chrome/browser/invalidation/invalidation_service_factory.h"
 #include "chrome/browser/policy/profile_policy_connector.h"
 #include "chrome/browser/policy/profile_policy_connector_factory.h"
 #include "chrome/browser/policy/test/local_policy_test_server.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/test/base/in_process_browser_test.h"
@@ skipping 280 matching lines @@
   // Perform the initial fetch.
   ASSERT_NO_FATAL_FAILURE(SetServerPolicy(GetTestPolicy("google.com", 0)));
   {
     base::RunLoop run_loop;
     policy_service->RefreshPolicies(run_loop.QuitClosure());
     run_loop.Run();
   }
 
   // Update the homepage in the policy and trigger an invalidation.
   ASSERT_NO_FATAL_FAILURE(SetServerPolicy(GetTestPolicy("youtube.com", 0)));
+  base::TimeDelta now =
+      base::Time::NowFromSystemTime() - base::Time::UnixEpoch();
   GetInvalidationService()->EmitInvalidationForTest(
       syncer::Invalidation::Init(
           invalidation::ObjectId(16, "test_policy"),
-          1 /* version */,
+          now.InMicroseconds() /* version */,
           "payload"));
   {
     base::RunLoop run_loop;
     on_policy_updated_ = run_loop.QuitClosure();
     run_loop.Run();
   }
 
   // Check that the updated policy was fetched.
   PolicyMap expected;
   GetExpectedTestPolicy(&expected, "youtube.com");
@@ skipping 96 matching lines @@
 
   // They should now serialize to the same bytes.
   std::string chrome_settings_serialized;
   std::string cloud_policy_serialized;
   ASSERT_TRUE(chrome_settings.SerializeToString(&chrome_settings_serialized));
   ASSERT_TRUE(cloud_policy.SerializeToString(&cloud_policy_serialized));
   EXPECT_EQ(chrome_settings_serialized, cloud_policy_serialized);
 }
 
 }  // namespace policy