[fuchsia] SetNavigationEventListener() immediately sends a NavigationState.

Bug: 979049
Change-Id: Ifa277e8cf1a76ddd00d76abbf8ac392eb7d0b9f9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1704692Reviewed-by: Wez <wez@chromium.org>
Commit-Queue: Fabrice de Gans-Riberi <fdegans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#682900}

fuchsia/engine/browser/frame_impl_browsertest.cc

@@ -1444,6 +1444,42 @@ IN_PROC_BROWSER_TEST_F(FrameImplTest, RecreateView) {
   navigation_listener_.RunUntilUrlAndTitleEquals(page1_url, kPage1Title);
 }
 
+// Tests SetNavigationEventListener() immediately returns a NavigationEvent,
+// even in the absence of a new navigation.
+IN_PROC_BROWSER_TEST_F(FrameImplTest, ImmediateNavigationEvent) {
+  ASSERT_TRUE(embedded_test_server()->Start());
+  GURL page_url(embedded_test_server()->GetURL(kPage1Path));
+
+  // The first NavigationState received should be empty.
+  base::RunLoop run_loop;
+  navigation_listener_.SetBeforeAckHook(base::BindRepeating(
+      [](base::RunLoop* run_loop, const fuchsia::web::NavigationState& change,
+         OnNavigationStateChangedCallback callback) {
+        EXPECT_TRUE(change.IsEmpty());
+        run_loop->Quit();
+        callback();
+      },
+      base::Unretained(&run_loop)));
+  fuchsia::web::FramePtr frame = CreateFrame();
+  run_loop.Run();
+  navigation_listener_.SetBeforeAckHook({});
+
+  // Navigate to a page and wait for the navigation to complete.
+  fuchsia::web::NavigationControllerPtr controller;
+  frame->GetNavigationController(controller.NewRequest());
+  EXPECT_TRUE(cr_fuchsia::LoadUrlAndExpectResponse(
+      controller.get(), fuchsia::web::LoadUrlParams(), page_url.spec()));
+  navigation_listener_.RunUntilUrlEquals(page_url);
+
+  // Attach a new navigation listener, we should get the new page state, even if
+  // no new navigation occurred.
+  cr_fuchsia::TestNavigationListener navigation_listener2;
+  fidl::Binding<fuchsia::web::NavigationEventListener>
+      navigation_listener_binding(&navigation_listener2);
+  frame->SetNavigationEventListener(navigation_listener_binding.NewBinding());
+  navigation_listener2.RunUntilUrlAndTitleEquals(page_url, kPage1Title);
+}
+
 class RequestMonitoringFrameImplBrowserTest : public FrameImplTest {
  public:
   RequestMonitoringFrameImplBrowserTest() = default;

fuchsia/engine/browser/navigation_controller_impl.cc

@@ -62,12 +62,26 @@ void NavigationControllerImpl::SetEventListener(
   previous_navigation_state_ = {};
   pending_navigation_event_ = {};
 
-  if (listener) {
-    navigation_listener_.Bind(std::move(listener));
-    navigation_listener_.set_error_handler(
-        [this](zx_status_t status) { SetEventListener(nullptr); });
-  } else {
+  // Simply unbind if no new listener was set.
+  if (!listener) {
     navigation_listener_.Unbind();
+    return;
+  }
+
+  navigation_listener_.Bind(std::move(listener));
+  navigation_listener_.set_error_handler(
+      [this](zx_status_t status) { SetEventListener(nullptr); });
+
+  // Immediately send the current navigation state, even if it is empty.
+  if (web_contents_->GetController().GetVisibleEntry() == nullptr) {
+    waiting_for_navigation_event_ack_ = true;
+    navigation_listener_->OnNavigationStateChanged(
+        fuchsia::web::NavigationState(), [this]() {
+          waiting_for_navigation_event_ack_ = false;
+          MaybeSendNavigationEvent();
+        });
+  } else {
+    OnNavigationEntryChanged();
   }
 }