[Sync] Implement support for updating storage key for new entities

components/sync/model_impl/processor_entity_tracker_unittest.cc

Index: components/sync/model_impl/processor_entity_tracker_unittest.cc
diff --git a/components/sync/model_impl/processor_entity_tracker_unittest.cc b/components/sync/model_impl/processor_entity_tracker_unittest.cc
index e23b9f581eacbdcb8d510a3e906e029a0ab949fb..e79e2850db989cc9211de88b952388155801dc02 100644
--- a/components/sync/model_impl/processor_entity_tracker_unittest.cc
+++ b/components/sync/model_impl/processor_entity_tracker_unittest.cc
@@ -107,6 +107,9 @@ class ProcessorEntityTrackerTest : public ::testing::Test {
   std::unique_ptr<ProcessorEntityTracker> CreateNew() {
     return ProcessorEntityTracker::CreateNew(kKey, kHash, "", ctime_);
   }
+  std::unique_ptr<ProcessorEntityTracker> CreateNewWithEmptyStorageKey() {
+    return ProcessorEntityTracker::CreateNew("", kHash, "", ctime_);
+  }
 
   std::unique_ptr<ProcessorEntityTracker> CreateSynced() {
     std::unique_ptr<ProcessorEntityTracker> entity = CreateNew();
@@ -242,6 +245,21 @@ TEST_F(ProcessorEntityTrackerTest, NewServerItem) {
   EXPECT_FALSE(entity->HasCommitData());
 }
 
+// Test creating tracker for new server item with empty storage key, applying
+// update and updating storage key.
+TEST_F(ProcessorEntityTrackerTest, NewServerItem_EmptyStorageKey) {
+  std::unique_ptr<ProcessorEntityTracker> entity =
+      CreateNewWithEmptyStorageKey();
+
+  EXPECT_EQ("", entity->storage_key());
+
+  const base::Time mtime = base::Time::Now();
+  entity->RecordAcceptedUpdate(
+      GenerateUpdate(*entity, kHash, kId, kName, kValue1, mtime, 10));
+  entity->SetStorageKey(kKey);
+  EXPECT_EQ(kKey, entity->storage_key());
+}
+
 // Test state for a tombstone received for a previously unknown item.
 TEST_F(ProcessorEntityTrackerTest, NewServerTombstone) {
   std::unique_ptr<ProcessorEntityTracker> entity = CreateNew();