[Sync] Stop updating local device info time stamp on merge.

components/sync/device_info/device_info_sync_bridge_unittest.cc

 // Copyright 2015 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/sync/device_info/device_info_sync_bridge.h"
 
 #include <algorithm>
 #include <set>
 #include <utility>
 
@@ skipping 645 matching lines @@
 
   const SyncError error = bridge()->MergeSyncData(
       bridge()->CreateMetadataChangeList(), remote_input);
   EXPECT_FALSE(error.IsSet());
   EXPECT_EQ(0, change_count());
   EXPECT_EQ(1u, bridge()->GetAllDeviceInfo().size());
   EXPECT_TRUE(processor()->delete_set().empty());
   EXPECT_TRUE(processor()->put_multimap().empty());
 }
 
+TEST_F(DeviceInfoSyncBridgeTest, MergeLocalGuidBeforeReconcile) {
+  InitializeBridge();
+  const DeviceInfoSpecifics specifics = CreateSpecifics(kDefaultLocalSuffix);
+
+  // The message loop is never pumped, which means local data/metadata is never
+  // loaded, and thus reconcile is never called. The bridge should ignore this
+  // EntityData because its cache guid is the same the local device's.
+  const SyncError error = bridge()->MergeSyncData(
+      bridge()->CreateMetadataChangeList(),
+      {{specifics.cache_guid(), SpecificsToEntity(specifics)}});
+  EXPECT_FALSE(error.IsSet());
+  EXPECT_EQ(0, change_count());
+  EXPECT_EQ(0u, bridge()->GetAllDeviceInfo().size());
+}
+
 TEST_F(DeviceInfoSyncBridgeTest, CountActiveDevices) {
   InitializeAndPump();
   EXPECT_EQ(1, bridge()->CountActiveDevices());
 
   DeviceInfoSpecifics specifics = CreateSpecifics(0);
   bridge()->ApplySyncChanges(bridge()->CreateMetadataChangeList(),
                              EntityAddList({specifics}));
   EXPECT_EQ(1, bridge()->CountActiveDevices());
 
   specifics.set_last_updated_timestamp(TimeToProtoTime(Time::Now()));
@@ skipping 68 matching lines @@
 
   // Reloading from storage shouldn't contain remote data.
   RestartBridge();
   EXPECT_EQ(1u, bridge()->GetAllDeviceInfo().size());
   EXPECT_EQ(4, change_count());
 }
 
 }  // namespace
 
 }  // namespace syncer