[Sync] Add a sanity integration test for USS.

components/sync/test/fake_server/tombstone_entity.cc

Index: components/sync/test/fake_server/tombstone_entity.cc
diff --git a/components/sync/test/fake_server/tombstone_entity.cc b/components/sync/test/fake_server/tombstone_entity.cc
index 20fa5355348b4a7977b6869411e8243bf5cc3f71..5da2feaea28b2927ef6d8875b76478cb13b0a2da 100644
--- a/components/sync/test/fake_server/tombstone_entity.cc
+++ b/components/sync/test/fake_server/tombstone_entity.cc
@@ -19,14 +19,19 @@ namespace fake_server {
 TombstoneEntity::~TombstoneEntity() {}
 
 // static
-std::unique_ptr<FakeServerEntity> TombstoneEntity::Create(const string& id) {
+std::unique_ptr<FakeServerEntity> TombstoneEntity::Create(
+    const string& id,
+    const string& client_defined_unique_tag) {
   const ModelType model_type = GetModelTypeFromId(id);
   CHECK_NE(model_type, syncer::UNSPECIFIED) << "Invalid ID was given: " << id;
-  return std::unique_ptr<FakeServerEntity>(new TombstoneEntity(id, model_type));
+  return std::unique_ptr<FakeServerEntity>(
+      new TombstoneEntity(id, client_defined_unique_tag, model_type));
 }
 
-TombstoneEntity::TombstoneEntity(const string& id, const ModelType& model_type)
-    : FakeServerEntity(id, model_type, 0, string()) {
+TombstoneEntity::TombstoneEntity(const string& id,
+                                 const string& client_defined_unique_tag,
+                                 const ModelType& model_type)
+    : FakeServerEntity(id, client_defined_unique_tag, model_type, 0, string()) {
   sync_pb::EntitySpecifics specifics;
   AddDefaultFieldValue(model_type, &specifics);
   SetSpecifics(specifics);