Environment

• Cross-platform modules: 6.1.0-next-2019-08-21-142040-01

Describe the bug
Since all changes to platform classes in #7606 are done through cssClasses property, they are not reflected in className property, thus changing className will overwrite them.

To Reproduce
Change root view className after running the app.

Expected behavior
CSS classes should be added both in cssClasses and className properties.