Expand overloaded methods and optional parameters in the html library.

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)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
   @DomName('IDBDatabase.createObjectStore')
   @DocsEditable
   ObjectStore createObjectStore(String name,
       {String keyPath, bool autoIncrement}) {
     var options = {};
     if (keyPath != null) {
       options['keyPath'] = keyPath;
     }
     if (autoIncrement != null) {
       options['autoIncrement'] = autoIncrement;
     }
 
     return $dom_createObjectStore(name, options);
   }
 
 $if DART2JS
-  Transaction transaction(storeName_OR_storeNames, String mode) {
+  Transaction transaction(String storeName, String mode) {
     if (mode != 'readonly' && mode != 'readwrite') {
       throw new ArgumentError(mode);
     }
-
-    // TODO(sra): Ensure storeName_OR_storeNames is a string or List<String>,
-    // and copy to JavaScript array if necessary.
-
     // Try and create a transaction with a string mode.  Browsers that expect a
     // numeric mode tend to convert the string into a number.  This fails
     // silently, resulting in zero ('readonly').
-    return _transaction(storeName_OR_storeNames, mode);
+    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 transactionStringList(DomStringList storeNames, String mode) {
+    if (mode != 'readonly' && mode != 'readwrite') {
+      throw new ArgumentError(mode);
+    }
+    return _transaction(storeNames_1, mode);
   }
 
   @JSName('transaction')
   Transaction _transaction(stores, mode) native;
 $endif
 
 $!MEMBERS}