fix(directive-injector): wrong variable name in error thrown.

Add proper type annotation that would have caught the typo.

Closes #1397
feat(scripts): pick-pr

Closes #1394
fix(perf_api): updgrade the pkg minimum version to fix an analyzer error

fixes #1407

perf_api 0.0.8 contains an invalid const constructor which the type
checker ignored in dart 1.5.8 but throws on in 1.6. Using 0.0.9 fixes
this.

Closes #1408
feat(directive injector): DiCircularDependencyError -> _CircularDependencyError

And make _CircularDependencyError extends CircularDependencyError
so that catching CircularDependencyError catches any circular dep
error

Closes #1399
chore: update pubspec.lock
feat(components): implement css encapsulation for transcluding components

* Extract ComponentCssLoader so it can be shared by ShadowDomComponentFactory and TranscludingComponentFactory
* Provide a built-in implementation of WebPlatformShim using css_shim
* Implement a CSS transformer similar to the one provided by Platform.JS
* Rename EventHandler into ShadowBoundary