re-swizzle build

This:

 * re-adds a compile task, which just does a simple dart2js compile of the two dart entrypoints
 * changes the archive task to archive the non-polymer version of the app
 * changes our test runner to prefer running the dart2js (non-polymer) app

It also enables the chrome+dart2js tests on the build bot.

@dinhviethoa @ussuri