[Sync] Add sync api support for context changes

sync/api/sync_data_unittest.cc

 // Copyright 2014 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 "sync/api/sync_data.h"
 
 #include <string>
 
 #include "base/time/time.h"
 #include "sync/protocol/sync.pb.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 using std::string;
 
 namespace syncer {
 
 namespace {
 
 const string kSyncTag = "3984729834";
 const ModelType kDatatype = syncer::PREFERENCES;
 const string kNonUniqueTitle = "my preference";
 const int64 kId = 439829;
 const base::Time kLastModifiedTime = base::Time();
+const std::string kContext = "context";
 
 typedef testing::Test SyncDataTest;
 
 TEST_F(SyncDataTest, NoArgCtor) {
   SyncData data;
   EXPECT_FALSE(data.IsValid());
 }
 
 TEST_F(SyncDataTest, CreateLocalDelete) {
   SyncData data = SyncData::CreateLocalDelete(kSyncTag, kDatatype);
   EXPECT_TRUE(data.IsValid());
   EXPECT_TRUE(data.IsLocal());
   EXPECT_EQ(kSyncTag, data.GetTag());
   EXPECT_EQ(kDatatype, data.GetDataType());
 }
 
 TEST_F(SyncDataTest, CreateLocalData) {
   sync_pb::EntitySpecifics specifics;
   specifics.mutable_preference();
   SyncData data =
       SyncData::CreateLocalData(kSyncTag, kNonUniqueTitle, specifics);
   EXPECT_TRUE(data.IsValid());
   EXPECT_TRUE(data.IsLocal());
   EXPECT_EQ(kSyncTag, data.GetTag());
   EXPECT_EQ(kDatatype, data.GetDataType());
   EXPECT_EQ(kNonUniqueTitle, data.GetTitle());
   EXPECT_TRUE(data.GetSpecifics().has_preference());
 }
 
+TEST_F(SyncDataTest, CreateContext) {
+  SyncData data = SyncData::CreateContext(kDatatype, kContext);
+  EXPECT_TRUE(data.IsValid());
+  EXPECT_EQ(data.GetContext(), kContext);
+
+  data = SyncData::CreateContext(kDatatype, "");
+  EXPECT_TRUE(data.IsValid());
+  EXPECT_EQ(data.GetContext(), "");
+}
+
 TEST_F(SyncDataTest, CreateRemoteData) {
   sync_pb::EntitySpecifics specifics;
   specifics.mutable_preference();
   SyncData data = SyncData::CreateRemoteData(kId, specifics, kLastModifiedTime);
   EXPECT_TRUE(data.IsValid());
   EXPECT_FALSE(data.IsLocal());
   EXPECT_EQ(kId, data.GetRemoteId());
   EXPECT_EQ(kLastModifiedTime, data.GetRemoteModifiedTime());
   EXPECT_TRUE(data.GetSpecifics().has_preference());
 }
 
 }  // namespace
 
 }  // namespace syncer