Ambient directives can be configured when bootstraping an application.
Ambient directives can be used in every component of the application without
needing to explicitly list them.
The test injector now uses an XHR implementation based on DOM.getXHR,
which allows the current DOM adapter to dictate which XHR impl should
be used.
To prevent the changes to DOM adapter from introducing undesired new
dependencies into the benchmarks, separate the async facade into
a promise facade which is reexported by facade/async.
See #4539
vsavkin
Julie Ralph