Switch IDB Database.transaction to use a template to do the right type conversions

tools/dom/templates/html/impl/impl_IDBDatabase.darttemplate

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of $LIBRARYNAME;
 
 @DocsEditable()
 $(ANNOTATIONS)$(NATIVESPEC)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS {
   @DomName('IDBDatabase.createObjectStore')
   @DocsEditable()
@@ skipping 35 matching lines @@
     return _transaction(storeName, mode);
   }
 
   Transaction transactionList(List<String> storeNames, String mode) {
     if (mode != 'readonly' && mode != 'readwrite') {
       throw new ArgumentError(mode);
     }
     List storeNames_1 = convertDartToNative_StringArray(storeNames);
     return _transaction(storeNames_1, mode);
   }
-  
+
   Transaction transactionStores(DomStringList storeNames, String mode) {
     if (mode != 'readonly' && mode != 'readwrite') {
       throw new ArgumentError(mode);
     }
     return _transaction(storeNames, mode);
   }
 
   @JSName('transaction')
   Transaction _transaction(stores, mode) native;
+$else
+  Transaction transaction(storeName_OR_storeNames, String mode) {
+    if (mode != 'readonly' && mode != 'readwrite') {
+      throw new ArgumentError("Invalid transaction mode $mode");
+    }
+    var names;
+    if (storeName_OR_storeNames == null) {
+      throw new ArgumentError("stores may not be null in transaction");
+    } else if (storeName_OR_storeNames is String || storeName_OR_storeNames is DomStringList) {
+      names = unwrap_jso(storeName_OR_storeNames);
+    } else if (storeName_OR_storeNames is List<String>) {
+      names = convertDartToNative_List(storeName_OR_storeNames);
+    } else {
+      throw new ArgumentError("Invalid store(s) $store_Name_OR_storeNames");
+    }
+
+    return wrap_jso(_blink.BlinkIDBDatabase.instance.transaction_Callback_2_(unwrap_jso(this), names, mode));
+  }
+
+  Transaction transactionList(List<String> storeNames, String mode) => transaction(storeNames, mode);
+  Transaction transactionStores(List<String> storeNames, String mode) => transaction(storeNames, mode);
+  Transaction transactionStore(String storeName, String mode) => transaction(storeName, mode);
 $endif
 
 $!MEMBERS}