refactor(router): don't run the change detection every time an outlet is activated

fix(router): inside on push // SQUASH after review

packages/router/src/router_outlet_context.ts

@@ -0,0 +1,80 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {ComponentFactoryResolver, ComponentRef} from '@angular/core';
+
+import {RouterOutlet} from './directives/router_outlet';
+import {ActivatedRoute} from './router_state';
+
+
+/**
+ * Store contextual information about a {@link RouterOutlet}
+ *
+ * @stable
+ */
+export class OutletContext {
+  outlet: RouterOutlet|null = null;
+  route: ActivatedRoute|null = null;
+  resolver: ComponentFactoryResolver|null = null;
+  children = new ChildrenOutletContexts();
+  attachRef: ComponentRef<any>|null = null;
+}
+
+/**
+ * Store contextual information about the children (= nested) {@link RouterOutlet}
+ *
+ * @stable
+ */
+export class ChildrenOutletContexts {
+  // contexts for child outlets, by name.
+  private contexts = new Map<string, OutletContext>();
+
+  /** Called when a `RouterOutlet` directive is instantiated */
+  onChildOutletCreated(childName: string, outlet: RouterOutlet): void {
+    const context = this.getOrCreateContext(childName);
+    context.outlet = outlet;
+    this.contexts.set(childName, context);
+  }
+
+  /**
+   * Called when a `RouterOutlet` directive is destroyed.
+   * We need to keep the context as the outlet could be destroyed inside a NgIf and might be
+   * re-created later.
+   */
+  onChildOutletDestroyed(childName: string): void {
+    const context = this.getContext(childName);
+    if (context) {
+      context.outlet = null;
+    }
+  }
+
+  /**
+   * Called when the corresponding route is deactivated during navigation.
+   * Because the component get destroyed, all children outlet are destroyed.
+   */
+  onOutletDeactivated(): Map<string, OutletContext> {
+    const contexts = this.contexts;
+    this.contexts = new Map();
+    return contexts;
+  }
+
+  onOutletReAttached(contexts: Map<string, OutletContext>) { this.contexts = contexts; }
+
+  getOrCreateContext(childName: string): OutletContext {
+    let context = this.getContext(childName);
+
+    if (!context) {
+      context = new OutletContext();
+      this.contexts.set(childName, context);
+    }
+
+    return context;
+  }
+
+  getContext(childName: string): OutletContext|null { return this.contexts.get(childName) || null; }
+}