Add tests for PresentationConnectionAvailable constructor.

third_party/WebKit/LayoutTests/presentation/resources/presentation-service-mock.js

+/*
+ * Mock implementation of mojo PresentationService.
+ */
+
+"use strict";
+
+let presentationServiceMock = loadMojoModules(
+    'presentationServiceMock',
+    [
+      'third_party/WebKit/public/platform/modules/presentation/presentation.mojom',
+      'mojo/public/js/router',
+    ]).then(mojo => {
+      let [ presentationService, router ] = mojo.modules;
+
+      class PresentationServiceMock {
+        constructor(interfaceProvider) {
+          interfaceProvider.addInterfaceOverrideForTesting(
+              presentationService.PresentationService.name,
+              handle => this.connectPresentationService_(handle));
+          this.interfaceProvider_ = interfaceProvider;
+          this.pendingResponse_ = null;
+        }
+
+        connectPresentationService_(handle) {
+          this.presentationServiceStub_ = new presentationService.PresentationService.stubClass(this);
+          this.presentationServiceRouter_ = new router.Router(handle);
+          this.presentationServiceRouter_.setIncomingReceiver(this.presentationServiceStub_);
+        }
+
+        startSession(urls) {
+          return Promise.resolve({
+              sessionInfo: { url: urls[0], id: 'fakesession' },
+              error: null,
+          });
+        }
+      }
+
+      return new PresentationServiceMock(mojo.frameInterfaces);
+    });