build(bazel): Turning on strictPropertyInitialization for Angular. (#24572)

All errors for existing fields have been detected and suppressed with a
`!` assertion.

Issue/24571 is tracking proper clean up of those instances.

One-line change required in ivy/compilation.ts, because it appears that
the new syntax causes tsickle emitted node to no longer track their
original sourceFiles.

PR Close #24572

packages/elements/src/component-factory-strategy.ts

@@ -44,10 +44,12 @@ export class ComponentNgElementStrategyFactory implements NgElementStrategyFacto
  */
 export class ComponentNgElementStrategy implements NgElementStrategy {
   /** Merged stream of the component's output events. */
-  events: Observable<NgElementStrategyEvent>;
+  // TODO(issue/24571): remove '!'.
+  events !: Observable<NgElementStrategyEvent>;
 
   /** Reference to the component that was created on connect. */
-  private componentRef: ComponentRef<any>|null;
+  // TODO(issue/24571): remove '!'.
+  private componentRef !: ComponentRef<any>| null;
 
   /** Changes that have been made to the component ref since the last time onChanges was called. */
   private inputChanges: SimpleChanges|null = null;

packages/elements/src/create-custom-element.ts

@@ -43,7 +43,8 @@ export abstract class NgElement extends HTMLElement {
   /**
    * The strategy that controls how a component is transformed in a custom element.
    */
-  protected ngElementStrategy: NgElementStrategy;
+  // TODO(issue/24571): remove '!'.
+  protected ngElementStrategy !: NgElementStrategy;
   /**
    * A subscription to change, connect, and disconnect events in the custom element.
    */

packages/elements/test/create-custom-element_spec.ts

@@ -103,7 +103,8 @@ if (typeof customElements !== 'undefined') {
 })
 class TestComponent {
   @Input() fooFoo: string = 'foo';
-  @Input('barbar') barBar: string;
+  // TODO(issue/24571): remove '!'.
+  @Input('barbar') barBar !: string;
 
   @Output() bazBaz = new EventEmitter<boolean>();
   @Output('quxqux') quxQux = new EventEmitter<Object>();