Test Extras Harness is not compatible with Sub Tree Rendering

[agubler]

Enhancement

The existing implementation of harness is not compatible with the sub tree rendering enhancements scheduled to land in @dojo/widget-core for the upcoming RC release. This is because the existing harness implementation depends on the existing internal rendering and invalidation logic. Sub tree rendering changes the algorithms for rendering/invalidation such that whole application widget tree will not always re-render when a widget somewhere in the tree invalidates.

The existing implementation cannot be fixed to work with these widget-core changes so will need to be re-designed and implemented from scratch. This provides an opportunity to re-think some of the original APIs and design decisions.

Sub Tree Rendering Pull Request