MD Settings: deflake back/forward navigation test via session restore

chrome/browser/ui/webui/settings/md_settings_ui_browsertest.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include <memory>
 #include <string>
+#include <vector>
 
 #include "chrome/browser/ui/browser.h"
-#include "chrome/browser/ui/browser_commands.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/common/url_constants.h"
 #include "chrome/test/base/in_process_browser_test.h"
 #include "chrome/test/base/ui_test_utils.h"
+#include "content/public/browser/navigation_controller.h"
+#include "content/public/browser/navigation_entry.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/browser/web_ui.h"
 #include "content/public/browser/web_ui_message_handler.h"
 #include "content/public/common/url_constants.h"
 #include "content/public/test/browser_test_utils.h"
 #include "ui/base/window_open_disposition.h"
 #include "url/gurl.h"
+#include "url/url_constants.h"
 
 typedef InProcessBrowserTest MdSettingsUITest;
 
 using ui_test_utils::NavigateToURL;
-using content::WaitForLoadStop;
 
 IN_PROC_BROWSER_TEST_F(MdSettingsUITest, ViewSourceDoesntCrash) {
   NavigateToURL(browser(),
       GURL(content::kViewSourceScheme + std::string(":") +
            chrome::kChromeUIMdSettingsURL));
 }
 
-// May not complete on memory bots. TODO(dbeam): investigate and fix.
-// See https://crbug.com/558434 and https://crbug.com/620370.
-#if defined(MEMORY_SANITIZER)
-#define MAYBE_BackForwardDoesntCrash DISABLED_BackForwardDoesntCrash
-#else
-#define MAYBE_BackForwardDoesntCrash BackForwardDoesntCrash
-#endif
+IN_PROC_BROWSER_TEST_F(MdSettingsUITest, BackForwardDoesntCrash) {
+  auto contents = browser()->tab_strip_model()->GetActiveWebContents();
 
-IN_PROC_BROWSER_TEST_F(MdSettingsUITest, MAYBE_BackForwardDoesntCrash) {
-  NavigateToURL(browser(), GURL(chrome::kChromeUIMdSettingsURL));
+  // Build some history.
+  std::vector<std::unique_ptr<content::NavigationEntry>> entries;
+  entries.push_back(content::NavigationController::CreateNavigationEntry(
+      GURL(url::kAboutBlankURL),
+      content::Referrer(),
+      ui::PAGE_TRANSITION_LINK,
+      true /* is_renderer_initiated */,
+      std::string() /* extra_headers */,
+      contents->GetBrowserContext()));
+  entries.push_back(content::NavigationController::CreateNavigationEntry(
+      GURL(chrome::kChromeUIMdSettingsURL),
+      content::Referrer(),
+      ui::PAGE_TRANSITION_LINK,
+      true /* is_renderer_initiated */,
+      std::string() /* extra_headers */,
+      contents->GetBrowserContext()));
 
-  NavigateToURL(browser(), GURL(chrome::kChromeUINewTabURL));
+  // Load the built history into the tab via session restore (which should load
+  // about:blank with chrome://md-settings as the URL to visit if forward is
+  // pressed).
+  contents->GetController().Restore(
+      0 /* selected_navigation */,
+      content::NavigationController::RESTORE_LAST_SESSION_EXITED_CLEANLY,
+      &entries);
+  ASSERT_EQ(0U, entries.size());
 
-  chrome::GoBack(browser(), CURRENT_TAB);
-  WaitForLoadStop(browser()->tab_strip_model()->GetActiveWebContents());
+  ASSERT_TRUE(contents->GetController().CanGoForward());
+  contents->GetController().GoForward();
+
+  // Go forward to visit chrome://md-settings.
+  ASSERT_TRUE(contents->GetController().CanGoForward());
+  contents->GetController().GoForward();
+
+  // TODO(dbeam): do we need to wait until load stop? Is there anything else we
+  // could wait for that reliably constructs handlers but is faster?
+  ASSERT_TRUE(content::WaitForLoadStop(contents));
+  EXPECT_EQ(GURL(chrome::kChromeUIMdSettingsURL),
+            contents->GetLastCommittedURL());
 }
 
 // Catch lifetime issues in message handlers. There was previously a problem
 // with PrefMember calling Init again after Destroy.
 IN_PROC_BROWSER_TEST_F(MdSettingsUITest, ToggleJavaScript) {
   NavigateToURL(browser(), GURL(chrome::kChromeUIMdSettingsURL));
 
   auto handlers = browser()->tab_strip_model()->GetActiveWebContents()
       ->GetWebUI()->GetHandlersForTesting();
 
   for (content::WebUIMessageHandler* handler : *handlers) {
     handler->AllowJavascriptForTesting();
     handler->DisallowJavascript();
     handler->AllowJavascriptForTesting();
   }
 }