sync: we can't lookup empty client tag nodes, so don't allow creating them

chrome/browser/sync/internal_api/syncapi_unittest.cc

Index: chrome/browser/sync/internal_api/syncapi_unittest.cc
diff --git a/chrome/browser/sync/internal_api/syncapi_unittest.cc b/chrome/browser/sync/internal_api/syncapi_unittest.cc
index 529867e22dd91700282b0ce4753bc221268d474d..b1c04a19eaeb53b7e59ff94e1e0644508c28ac05 100644
--- a/chrome/browser/sync/internal_api/syncapi_unittest.cc
+++ b/chrome/browser/sync/internal_api/syncapi_unittest.cc
@@ -690,6 +690,17 @@ TEST_F(SyncApiTest, ChangeRecordToValue) {
   }
 }
 
+TEST_F(SyncApiTest, EmptyTags) {
+  WriteTransaction trans(FROM_HERE, test_user_share_.user_share());
+  ReadNode root_node(&trans);
+  root_node.InitByRootLookup();
+  WriteNode node(&trans);
+  std::string empty_tag;
+  EXPECT_FALSE(node.InitUniqueByCreation(
+      syncable::TYPED_URLS, root_node, empty_tag));
+  EXPECT_FALSE(node.InitByTagLookup(empty_tag));
+}
+
 namespace {
 
 class TestHttpPostProviderInterface : public HttpPostProviderInterface {