[Nav Experiment] Fix forward navigation after restore.

Navigation entries restored from a previously saved session are inserted
as restore_session.html?targetUrl=<target> URLs. The onload handler
redirects the page to the target URL when loaded. It turns out that
WKWebView does not fire onload handler in back/forward navigation
from an about:blank URL redirected from restore_session.html to another
restore_session.html. Most likely it's because WkWebView consiters this
a same-page navigation. This causes forward navigationt from a restored
app-specific URL to not load the web content.

This CL fixes it by forcing a reload in the WKWebView in this case.

Bug: 814790
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: Ie6e7ada39388cedd7357a582308f0edc1397ef63
Reviewed-on: https://chromium-review.googlesource.com/974365Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Danyao Wang <danyao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#545166}

ios/chrome/browser/web/browsing_egtest.mm

@@ -13,7 +13,6 @@
 #include "ios/chrome/browser/ui/ui_util.h"
 #include "ios/chrome/grit/ios_strings.h"
 #import "ios/chrome/test/app/chrome_test_util.h"
-#include "ios/chrome/test/app/navigation_test_util.h"
 #import "ios/chrome/test/app/web_view_interaction_test_util.h"
 #import "ios/chrome/test/earl_grey/chrome_earl_grey.h"
 #import "ios/chrome/test/earl_grey/chrome_earl_grey_ui.h"

ios/chrome/browser/web/navigation_egtest.mm

@@ -7,6 +7,7 @@
 #include "base/ios/ios_util.h"
 #include "components/strings/grit/components_strings.h"
 #import "ios/chrome/browser/ui/uikit_ui_util.h"
+#import "ios/chrome/test/app/chrome_test_util.h"
 #import "ios/chrome/test/app/web_view_interaction_test_util.h"
 #import "ios/chrome/test/earl_grey/chrome_earl_grey.h"
 #import "ios/chrome/test/earl_grey/chrome_matchers.h"
@@ -22,6 +23,7 @@
 using chrome_test_util::ContentSuggestionCollectionView;
 using chrome_test_util::BackButton;
 using chrome_test_util::ForwardButton;
+using chrome_test_util::PurgeCachedWebViewPages;
 using chrome_test_util::OmniboxText;
 using chrome_test_util::TapWebViewElementWithId;
 
@@ -594,4 +596,40 @@ std::unique_ptr<net::test_server::HttpResponse> WindowLocationHashHandlers(
       assertWithMatcher:grey_notNil()];
 }
 
+// Tests that navigating forward from a WebUI URL works when resuming from
+// session restore. This is a regression test for https://crbug.com/814790.
+- (void)testRestoreHistoryToWebUIAndNavigateForward {
+  GREYAssertTrue(self.testServer->Start(), @"Test server failed to start.");
+  const GURL destinationURL = self.testServer->GetURL(kSimpleFileBasedTestURL);
+  [ChromeEarlGrey loadURL:GURL("chrome://version")];
+  [ChromeEarlGrey loadURL:destinationURL];
+  [ChromeEarlGrey goBack];
+
+  GREYAssert(PurgeCachedWebViewPages(), @"History not restored");
+
+  [ChromeEarlGrey waitForWebViewContainingText:"Revision"];
+  [[EarlGrey selectElementWithMatcher:OmniboxText("chrome://version")]
+      assertWithMatcher:grey_notNil()];
+  [ChromeEarlGrey goForward];
+  [ChromeEarlGrey waitForWebViewContainingText:"pony"];
+  [[EarlGrey selectElementWithMatcher:OmniboxText(destinationURL.GetContent())]
+      assertWithMatcher:grey_notNil()];
+}
+
+// Tests that navigating forward from NTP works when resuming from session
+// restore. This is a regression test for https://crbug.com/814790.
+- (void)testRestoreHistoryToNTPAndNavigateForward {
+  GREYAssertTrue(self.testServer->Start(), @"Test server failed to start.");
+  const GURL destinationURL = self.testServer->GetURL(kSimpleFileBasedTestURL);
+  [ChromeEarlGrey loadURL:destinationURL];
+  [ChromeEarlGrey goBack];
+
+  GREYAssert(PurgeCachedWebViewPages(), @"History not restored");
+
+  [ChromeEarlGrey goForward];
+  [ChromeEarlGrey waitForWebViewContainingText:"pony"];
+  [[EarlGrey selectElementWithMatcher:OmniboxText(destinationURL.GetContent())]
+      assertWithMatcher:grey_notNil()];
+}
+
 @end

ios/chrome/browser/web/visible_url_egtest.mm

@@ -31,6 +31,7 @@
 #endif
 
 using chrome_test_util::OmniboxText;
+using chrome_test_util::PurgeCachedWebViewPages;
 
 namespace {
 
@@ -45,19 +46,6 @@ const char kPage1Link[] = "page-1";
 const char kPage2Link[] = "page-2";
 const char kPage3Link[] = "page-3";
 
-// Purges cached web view page, so the next time back navigation will not use
-// cached page. Browsers don't have to use fresh version for back forward
-// navigation for HTTP pages and may serve version from the cache even if
-// Cache-Control response header says otherwise.
-bool PurgeCachedWebViewPages() WARN_UNUSED_RESULT;
-bool PurgeCachedWebViewPages() {
-  web::WebState* web_state = chrome_test_util::GetCurrentWebState();
-  web_state->SetWebUsageEnabled(false);
-  web_state->SetWebUsageEnabled(true);
-  web_state->GetNavigationManager()->LoadIfNecessary();
-  return chrome_test_util::WaitForPageToFinishLoading();
-}
-
 // Response provider which can be paused. When it is paused it buffers all
 // requests and does not respond to them until |set_paused(false)| is called.
 class PausableResponseProvider : public HtmlResponseProvider {

ios/chrome/test/app/chrome_test_util.h

@@ -97,6 +97,12 @@ void WaitForBreakpadQueue();
 // Simulates launching Chrome from another application.
 void OpenChromeFromExternalApp(const GURL& url);
 
+// Purges cached web view page, so the next time back navigation will not use
+// cached page. Browsers don't have to use fresh version for back forward
+// navigation for HTTP pages and may serve version from the cache even if
+// Cache-Control response header says otherwise.
+bool PurgeCachedWebViewPages() WARN_UNUSED_RESULT;
+
 }  // namespace chrome_test_util
 
 #endif  // IOS_CHROME_TEST_APP_CHROME_TEST_UTIL_H_

ios/chrome/test/app/chrome_test_util.mm

@@ -24,7 +24,9 @@
 #import "ios/chrome/browser/ui/main/view_controller_swapping.h"
 #import "ios/chrome/browser/ui/ntp/new_tab_page_controller.h"
 #import "ios/chrome/browser/ui/tab_switcher/tab_switcher.h"
+#include "ios/chrome/test/app/navigation_test_util.h"
 #import "ios/chrome/test/app/tab_test_util.h"
+#import "ios/web/public/navigation_manager.h"
 #import "ios/web/public/test/native_controller_test_util.h"
 #import "third_party/breakpad/breakpad/src/client/ios/BreakpadController.h"
 
@@ -231,4 +233,12 @@ void OpenChromeFromExternalApp(const GURL& url) {
       applicationDidBecomeActive:[UIApplication sharedApplication]];
 }
 
+bool PurgeCachedWebViewPages() {
+  web::WebState* web_state = chrome_test_util::GetCurrentWebState();
+  web_state->SetWebUsageEnabled(false);
+  web_state->SetWebUsageEnabled(true);
+  web_state->GetNavigationManager()->LoadIfNecessary();
+  return chrome_test_util::WaitForPageToFinishLoading();
+}
+
 }  // namespace chrome_test_util

ios/web/web_state/ui/crw_web_controller.mm

@@ -4929,12 +4929,29 @@ registerLoadRequestForURL:(const GURL&)requestURL
 }
 
 - (void)webViewLoadingStateDidChange {
-  if ([_webView isLoading] || ![self isCurrentNavigationBackForward]) {
+  if (_webView.loading)
     return;
-  }
 
   GURL webViewURL = net::GURLWithNSURL([_webView URL]);
 
+  // When traversing history restored from a previous session, WKWebView does
+  // not fire 'pageshow', 'onload', 'popstate' or any of the
+  // WKNavigationDelegate callbacks for back/forward navigation from an
+  // app-specific URL to another entry. Loading state KVO is the only observable
+  // event in this scenario, so force a reload to trigger redirect from
+  // restore_session.html to the restored URL.
+  bool previousURLIsAppSpecific =
+      IsPlaceholderUrl(_documentURL) ||
+      web::GetWebClient()->IsAppSpecificURL(_documentURL);
+  if (web::GetWebClient()->IsSlimNavigationManagerEnabled() &&
+      web::IsRestoreSessionUrl(webViewURL) && previousURLIsAppSpecific) {
+    [_webView reload];
+    return;
+  }
+
+  if (![self isCurrentNavigationBackForward])
+    return;
+
   // For failed navigations, WKWebView will sometimes revert to the previous URL
   // before committing the current navigation or resetting the web view's
   // |isLoading| property to NO.  If this is the first navigation for the web