base: Remove the string logging from CHECK().

components/sync/test/fake_server/unique_client_entity.cc

Index: components/sync/test/fake_server/unique_client_entity.cc
diff --git a/components/sync/test/fake_server/unique_client_entity.cc b/components/sync/test/fake_server/unique_client_entity.cc
index 346a2ae07785e7b88676a09e082c8023ac4110ec..538214676f40ff0c9bb7377f082e31d33a3f41b2 100644
--- a/components/sync/test/fake_server/unique_client_entity.cc
+++ b/components/sync/test/fake_server/unique_client_entity.cc
@@ -51,8 +51,8 @@ UniqueClientEntity::~UniqueClientEntity() {}
 // static
 std::unique_ptr<FakeServerEntity> UniqueClientEntity::Create(
     const sync_pb::SyncEntity& client_entity) {
-  CHECK(client_entity.has_client_defined_unique_tag())
-      << "A UniqueClientEntity must have a client-defined unique tag.";
+  // A UniqueClientEntity must have a client-defined unique tag.
+  CHECK(client_entity.has_client_defined_unique_tag());
   ModelType model_type =
       syncer::GetModelTypeFromSpecifics(client_entity.specifics());
   string id = EffectiveIdForClientTaggedEntity(client_entity);