Update the Angular 2 transformer to recognize
`package:angular2/platform/browser.dart` as the library which exports
the `bootstrap` function.
Update playground, examples, benchmarks, & tests to import bootstrap from
platform/browser.
Closes#7647
The hello_world app used to measure Dart payload size was broken by a
change in
7ae23adaff.
This breakage does not materially affect the size of the generated code,
(before fix: 298819, after fix: 298825), and since it was a runtime
error it was not noticed & not a problem.
Update the app to work again.
Closes#7358
Import dependencies from `angular2/angular2.dart` in `hello_world` to
ensure that any size regressions are caught by our checks.
Update to avoid regressions like #5419.
Closes#5394