feat(core): Add type information to injector.get() (#13785)

- Introduce `InjectionToken<T>` which is a parameterized and type-safe
  version of `OpaqueToken`.

DEPRECATION:
- `OpaqueToken` is now deprecated, use `InjectionToken<T>` instead.
- `Injector.get(token: any, notFoundValue?: any): any` is now deprecated
  use the same method which is now overloaded as
  `Injector.get<T>(token: Type<T>|InjectionToken<T>, notFoundValue?: T): T;`.

Migration
- Replace `OpaqueToken` with `InjectionToken<?>` and parameterize it.
- Migrate your code to only use `Type<?>` or `InjectionToken<?>` as
  injection tokens. Using other tokens will not be supported in the
  future.

BREAKING CHANGE:
- Because `injector.get()` is now parameterize it is possible that code
  which used to work no longer type checks. Example would be if one
  injects `Foo` but configures it as `{provide: Foo, useClass: MockFoo}`.
  The injection instance will be that of `MockFoo` but the type will be
  `Foo` instead of `any` as in the past. This means that it was possible
  to call a method on `MockFoo` in the past which now will fail type
  check. See this example:

```
class Foo {}
class MockFoo extends Foo {
  setupMock();
}

var PROVIDERS = [
  {provide: Foo, useClass: MockFoo}
];

...

function myTest(injector: Injector) {
  var foo = injector.get(Foo);
  // This line used to work since `foo` used to be `any` before this
  // change, it will now be `Foo`, and `Foo` does not have `setUpMock()`.
  // The fix is to downcast: `injector.get(Foo) as MockFoo`.
  foo.setUpMock();
}
```

PR Close #13785

modules/@angular/platform-webworker/src/web_workers/shared/api.ts

@@ -6,6 +6,6 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {OpaqueToken} from '@angular/core';
+import {InjectionToken} from '@angular/core';
 
-export const ON_WEB_WORKER = new OpaqueToken('WebWorker.onWebWorker');
+export const ON_WEB_WORKER = new InjectionToken('WebWorker.onWebWorker');

modules/@angular/platform-webworker/src/web_workers/worker/location_providers.ts

@@ -7,11 +7,12 @@
  */
 
 import {PlatformLocation} from '@angular/common';
-import {APP_INITIALIZER, NgZone} from '@angular/core';
+import {APP_INITIALIZER, InjectionToken, NgZone} from '@angular/core';
 
 import {WebWorkerPlatformLocation} from './platform_location';
 
 
+
 /**
  * Those providers should be added when the router is used in a worker context in addition to the
  * {@link ROUTER_PROVIDERS} and after them.

modules/@angular/platform-webworker/src/worker_render.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {ErrorHandler, Injectable, Injector, NgZone, OpaqueToken, PLATFORM_INITIALIZER, PlatformRef, Provider, RootRenderer, Testability, createPlatformFactory, isDevMode, platformCore} from '@angular/core';
+import {ErrorHandler, Injectable, InjectionToken, Injector, NgZone, PLATFORM_INITIALIZER, PlatformRef, Provider, RootRenderer, Testability, createPlatformFactory, isDevMode, platformCore} from '@angular/core';
 import {AnimationDriver, DOCUMENT, EVENT_MANAGER_PLUGINS, EventManager, HAMMER_GESTURE_CONFIG, HammerGestureConfig} from '@angular/platform-browser';
 
 import {APP_ID_RANDOM_PROVIDER} from './private_import_core';
@@ -21,6 +21,7 @@ import {ServiceMessageBrokerFactory, ServiceMessageBrokerFactory_} from './web_w
 import {MessageBasedRenderer} from './web_workers/ui/renderer';
 
 
+
 /**
  * Wrapper class that exposes the Worker
  * and underlying {@link MessageBus} for lower level message passing.
@@ -42,7 +43,7 @@ export class WebWorkerInstance {
 /**
  * @experimental WebWorker support is currently experimental.
  */
-export const WORKER_SCRIPT: OpaqueToken = new OpaqueToken('WebWorkerScript');
+export const WORKER_SCRIPT = new InjectionToken<string>('WebWorkerScript');
 
 /**
  * A multi-provider used to automatically call the `start()` method after the service is
@@ -52,7 +53,7 @@ export const WORKER_SCRIPT: OpaqueToken = new OpaqueToken('WebWorkerScript');
  * @experimental WebWorker support is currently experimental.
  */
 export const WORKER_UI_STARTABLE_MESSAGING_SERVICE =
-    new OpaqueToken('WorkerRenderStartableMsgService');
+    new InjectionToken<MessageBasedRenderer[]>('WorkerRenderStartableMsgService');
 
 export const _WORKER_UI_PLATFORM_PROVIDERS: Provider[] = [
   {provide: NgZone, useFactory: createNgZone, deps: []},