This demo doesn't work properly in landscape and is confusing. It's
really more of a test of the material arc code.

Fixes #5710

Added a demo of BottomNavigation to the Gallery.

* turn verbs into nouns for gallery homepage

* shorter is better

Closes #5702

Update transitions_perf_test.dart

Update simple_smoke_test.dart

*  Gallery demo start-time performance test

Use the route table to generate the list of screens to test in the smoke test.