Made index_db Cursor.next behavior consistent between JS and vm.

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

Index: tools/dom/templates/html/impl/impl_IDBCursor.darttemplate
diff --git a/tools/dom/templates/html/impl/impl_IDBCursor.darttemplate b/tools/dom/templates/html/impl/impl_IDBCursor.darttemplate
index 35ae804ee5186f375b543096fa24a73111f9ea64..70689f8ce2831cf25467f94f21338e14d6ffbdac 100644
--- a/tools/dom/templates/html/impl/impl_IDBCursor.darttemplate
+++ b/tools/dom/templates/html/impl/impl_IDBCursor.darttemplate
@@ -23,5 +23,16 @@ $(ANNOTATIONS)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
     }
   }
 
+  $if DART2JS
+  @JSName('continue')
+  @DomName('IDBCursor.continue')
+  void next([Object key]) {
+    if (key == null) {
+      JS('void', '#.continue()', this);
+    } else {
+      JS('void', '#.continue(#)', this, key);
+    }
+  }
+  $endif
   $!MEMBERS
 }