Fix bug when a NavigationThrottle blocks a request during a redirect.

content/browser/frame_host/navigation_handle_impl_browsertest.cc

Index: content/browser/frame_host/navigation_handle_impl_browsertest.cc
diff --git a/content/browser/frame_host/navigation_handle_impl_browsertest.cc b/content/browser/frame_host/navigation_handle_impl_browsertest.cc
index 82f3c8cb4cfb2a5091ac7ecedee6bd85c1cf7639..5a8f794b8433cab61e665e5d01e59f15589ced4c 100644
--- a/content/browser/frame_host/navigation_handle_impl_browsertest.cc
+++ b/content/browser/frame_host/navigation_handle_impl_browsertest.cc
@@ -1067,4 +1067,63 @@ IN_PROC_BROWSER_TEST_F(NavigationHandleImplBrowserTest,
   }
 }
 
+// Record and list the navigations that are started and finished.
+class NavigationLogger : public WebContentsObserver {
+ public:
+  NavigationLogger(WebContents* web_contents)
+      : WebContentsObserver(web_contents) {}
+
+  void DidStartNavigation(NavigationHandle* navigation_handle) override {
+    started_navigation_urls_.push_back(navigation_handle->GetURL());
+  }
+
+  void DidFinishNavigation(NavigationHandle* navigation_handle) override {
+    finished_navigation_urls_.push_back(navigation_handle->GetURL());
+  }
+
+  const std::vector<GURL>& GetStartedNavigationURLS() {
+    return started_navigation_urls_;
+  }
+  const std::vector<GURL>& GetFinishedNavigationURLS() {
+    return finished_navigation_urls_;
+  }
+
+ private:
+  std::vector<GURL> started_navigation_urls_;
+  std::vector<GURL> finished_navigation_urls_;
+};
+
+// There was a bug without PlzNavigate that happened when a navigation was
+// blocked after a redirect. Blink didn't know about the redirect and tried
+// to commit an error page to the post-redirect URL. The result was that the
+// NavigationHandle was not found on the browser-side and a new NavigationHandle
+// created for committing the error page. This test makes sure that only one
+// NavigationHandle is used for committing the error page.
+// See crbug.com/695421
+IN_PROC_BROWSER_TEST_F(NavigationHandleImplBrowserTest, BlockedOnRedirect) {
+  const GURL kUrl = embedded_test_server()->GetURL("/title1.html");
+  const GURL kRedirectingUrl =
+      embedded_test_server()->GetURL("/server-redirect?" + kUrl.spec());
+
+  // Set up a NavigationThrottle that will block the navigation in
+  // WillRedirectRequest.
+  TestNavigationThrottleInstaller installer(
+      shell()->web_contents(), NavigationThrottle::PROCEED,
+      NavigationThrottle::BLOCK_REQUEST, NavigationThrottle::PROCEED);
+  NavigationHandleObserver observer(shell()->web_contents(), kRedirectingUrl);
+  NavigationLogger logger(shell()->web_contents());
+
+  // Try to navigate to the url. The navigation should be canceled and the
+  // NavigationHandle should have the right error code.
+  EXPECT_FALSE(NavigateToURL(shell(), kRedirectingUrl));
+  EXPECT_EQ(net::ERR_BLOCKED_BY_CLIENT, observer.net_error_code());
+
+  // Only one navigation is expected to happen.
+  std::vector<GURL> started_navigation = {kRedirectingUrl};
+  EXPECT_EQ(started_navigation, logger.GetStartedNavigationURLS());
+
+  std::vector<GURL> finished_navigation = {kUrl};
+  EXPECT_EQ(finished_navigation, logger.GetFinishedNavigationURLS());
+}
+
 }  // namespace content