
Polymer linter doesn't process Polymer.mixinBehaviors(...) correctly. This will lead to a problem after swtiching to a class-based components. To workaround these issue, the mock mixins are added as a temporary solution. After converting to a class-based element, all behaviors will be converted to mixin classes. Change-Id: I8dc3cb9767be3aa08c67fedbff77105e4b8b4ec1