This commit introduces a new API to the ngUpgrade module, which is compatible
with AoT compilation. Primarily, it removes the dependency on reflection
over the Angular 2 metadata by introducing an API where this information
is explicitly defined, in the source code, in a way that is not lost through
AoT compilation.
This commit is a collaboration between @mhevery (who provided the original
design of the API); @gkalpak & @petebacondarwin (who implemented the
API and migrated the specs from the original ngUpgrade tests) and @alexeagle
(who provided input and review).
This commit is an starting point, there is still work to be done:
* add more documentation
* validate the API via internal projects
* align the ngUpgrade compilation of A1 directives closer to the real A1
compiler
* add more unit tests
* consider support for async `templateUrl` A1 upgraded components
Closes#12239
Currently downgraded ng2 elements fail inside a ui-router view because they are unable
to require an ng2 Injector via the require attribute of the DDO, because ui-router compiles
its templates before they are inserted in a ui-view. This adds a "fallback" behavior if
a parent injector cannot be found to go to the root ng2 Injector.
