cros: Preload and reuse the lock screen across lock sessions

This is currently behind a feature flag and not enabled by default.

- The lock screen webview will be saved and reused across lock sessions.
- The lock screen webview will be preloaded after the user has not generated any input events for 8 seconds.

See https://codereview.chromium.org/2512473004/ for additional context.

BUG=669638

Review-Url: https://codereview.chromium.org/2553863002
Cr-Commit-Position: refs/heads/master@{#438698}

chrome/browser/chromeos/login/lock/webui_screen_locker.cc

@@ -8,6 +8,7 @@
 #include "ash/shell.h"
 #include "ash/system/chromeos/power/power_event_observer.h"
 #include "base/command_line.h"
+#include "base/feature_list.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/values.h"
@@ -16,19 +17,29 @@
 #include "chrome/browser/chromeos/accessibility/accessibility_util.h"
 #include "chrome/browser/chromeos/login/helper.h"
 #include "chrome/browser/chromeos/login/lock/screen_locker.h"
+#include "chrome/browser/chromeos/login/ui/shared_web_view.h"
+#include "chrome/browser/chromeos/login/ui/shared_web_view_factory.h"
+#include "chrome/browser/chromeos/login/ui/web_view_handle.h"
 #include "chrome/browser/chromeos/login/ui/webui_login_display.h"
+#include "chrome/browser/chromeos/profiles/profile_helper.h"
 #include "chrome/browser/ui/webui/chromeos/login/oobe_ui.h"
 #include "chrome/browser/ui/webui/chromeos/login/signin_screen_handler.h"
+#include "chrome/common/chrome_features.h"
+#include "chrome/common/pref_names.h"
 #include "chrome/common/url_constants.h"
+#include "chrome/grit/generated_resources.h"
 #include "chromeos/dbus/dbus_thread_manager.h"
+#include "components/prefs/pref_service.h"
 #include "components/user_manager/user.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/notification_types.h"
 #include "content/public/browser/render_widget_host_view.h"
+#include "content/public/browser/web_contents.h"
 #include "content/public/browser/web_ui.h"
 #include "ui/aura/client/capture_client.h"
 #include "ui/aura/window_event_dispatcher.h"
+#include "ui/base/l10n/l10n_util.h"
 #include "ui/base/x/x11_util.h"
 #include "ui/display/display.h"
 #include "ui/display/screen.h"
@@ -53,15 +64,61 @@ void ResetKeyboardOverscrollOverride() {
       keyboard::KEYBOARD_OVERSCROLL_OVERRIDE_NONE);
 }
 
+chromeos::WebUILoginView::WebViewSettings BuildSettings() {
+  chromeos::WebUILoginView::WebViewSettings settings;
+  if (chromeos::WebUIScreenLocker::ShouldShareLockScreen()) {
+    settings.preloaded_url = GURL(kLoginURL);
+    settings.web_view_title =
+        l10n_util::GetStringUTF16(IDS_LOCK_SCREEN_TASK_MANAGER_NAME);
+  }
+  return settings;
+}
+
 }  // namespace
 
 namespace chromeos {
 
+// static
+bool WebUIScreenLocker::ShouldShareLockScreen() {
+  Profile* profile = ProfileHelper::Get()->GetProfileByUser(
+      user_manager::UserManager::Get()->GetActiveUser());
+
+  // We only want to share the lock screen if the user is likely to see the lock
+  // screen (since caching the lock screen uses memory). Without preloading,
+  // showing the lock screen can take so long we will timeout and crash the
+  // browser process (which currently takes down all of Chrome). See
+  // crbug.com/452599 for more context.
+  //
+  // prefs::kEnableAutoScreenLock controls if the lock screen is shown on
+  // suspend, so that is our primary hueristic.
+
+  // Note that |profile| can be null in tests.
+  return base::FeatureList::IsEnabled(features::kSharedLockScreen) && profile &&
+         profile->GetPrefs()->GetBoolean(prefs::kEnableAutoScreenLock);
+}
+
+// static
+void WebUIScreenLocker::Preload() {
+  DCHECK(ShouldShareLockScreen());
+  VLOG(1) << "Preloading lock screen";
+
+  SharedWebView* shared_web_view =
+      SharedWebViewFactory::GetForProfile(ProfileHelper::GetSigninProfile());
+
+  scoped_refptr<WebViewHandle> web_view_handle;
+  if (!shared_web_view->Get(GURL(kLoginURL), &web_view_handle)) {
+    web_view_handle->web_view()->LoadInitialURL(GURL(kLoginURL));
+    InitializeWebView(
+        web_view_handle->web_view(),
+        l10n_util::GetStringUTF16(IDS_LOCK_SCREEN_TASK_MANAGER_NAME));
+  }
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // WebUIScreenLocker implementation.
 
 WebUIScreenLocker::WebUIScreenLocker(ScreenLocker* screen_locker)
-    : WebUILoginView(WebViewSettings()),
+    : WebUILoginView(BuildSettings()),
       screen_locker_(screen_locker),
       network_state_helper_(new login::NetworkStateHelper),
       weak_factory_(this) {

chrome/browser/chromeos/login/lock/webui_screen_locker.h

@@ -55,6 +55,10 @@ class WebUIScreenLocker : public WebUILoginView,
                           public display::DisplayObserver,
                           public content::WebContentsObserver {
  public:
+  // Returns true if the lock screen should be shared.
+  static bool ShouldShareLockScreen();
+  static void Preload();
+
   explicit WebUIScreenLocker(ScreenLocker* screen_locker);
   ~WebUIScreenLocker() override;
 

chrome/browser/chromeos/login/session/chrome_session_manager.cc

@@ -17,6 +17,8 @@
 #include "chrome/browser/chromeos/app_mode/kiosk_app_manager.h"
 #include "chrome/browser/chromeos/arc/arc_service_launcher.h"
 #include "chrome/browser/chromeos/boot_times_recorder.h"
+#include "chrome/browser/chromeos/idle_detector.h"
+#include "chrome/browser/chromeos/login/lock/webui_screen_locker.h"
 #include "chrome/browser/chromeos/login/login_wizard.h"
 #include "chrome/browser/chromeos/login/session/user_session_manager.h"
 #include "chrome/browser/chromeos/login/wizard_controller.h"
@@ -44,6 +46,9 @@ namespace chromeos {
 
 namespace {
 
+// Duration of user inactivity before preloading the lock screen.
+constexpr int kIdleSecondsBeforePreloadingLockScreen = 8;
+
 // Whether kiosk auto launch should be started.
 bool ShouldAutoLaunchKioskApp(const base::CommandLine& command_line) {
   KioskAppManager* app_manager = KioskAppManager::Get();
@@ -232,6 +237,13 @@ void ChromeSessionManager::SessionStarted() {
       content::Source<session_manager::SessionManager>(this),
       content::Details<const user_manager::User>(
           user_manager->GetActiveUser()));
+
+  if (chromeos::WebUIScreenLocker::ShouldShareLockScreen()) {
+    idle_detector_ = base::MakeUnique<chromeos::IdleDetector>(
+        base::Bind(&chromeos::WebUIScreenLocker::Preload));
+    idle_detector_->Start(
+        base::TimeDelta::FromSeconds(kIdleSecondsBeforePreloadingLockScreen));
+  }
 }
 
 void ChromeSessionManager::NotifyUserLoggedIn(const AccountId& user_account_id,

chrome/browser/chromeos/login/session/chrome_session_manager.h

@@ -16,6 +16,8 @@ class Profile;
 
 namespace chromeos {
 
+class IdleDetector;
+
 class ChromeSessionManager : public session_manager::SessionManager {
  public:
   ChromeSessionManager();
@@ -38,6 +40,9 @@ class ChromeSessionManager : public session_manager::SessionManager {
                           bool browser_restart) override;
 
  private:
+  // Used to preload the lock screen when the user is inactive.
+  std::unique_ptr<IdleDetector> idle_detector_;
+
   DISALLOW_COPY_AND_ASSIGN(ChromeSessionManager);
 };
 

chrome/common/chrome_features.cc

@@ -194,6 +194,13 @@ const base::Feature kRunAllFlashInAllowMode{"RunAllFlashInAllowMode",
 const base::Feature kSafeSearchUrlReporting{"SafeSearchUrlReporting",
                                             base::FEATURE_DISABLED_BY_DEFAULT};
 
+#if defined(OS_CHROMEOS)
+// The lock screen will be preloaded and shared so it is instantly available
+// when the user locks the Chromebook device.
+const base::Feature kSharedLockScreen{"SharedLockScreen",
+                                      base::FEATURE_DISABLED_BY_DEFAULT};
+#endif
+
 // A new user experience for transitioning into fullscreen and mouse pointer
 // lock states.
 const base::Feature kSimplifiedFullscreenUI{"ViewsSimplifiedFullscreenUI",

chrome/common/chrome_features.h

@@ -115,6 +115,10 @@ extern const base::Feature kRunAllFlashInAllowMode;
 
 extern const base::Feature kSafeSearchUrlReporting;
 
+#if defined(OS_CHROMEOS)
+extern const base::Feature kSharedLockScreen;
+#endif
+
 extern const base::Feature kSimplifiedFullscreenUI;
 
 #if defined(SYZYASAN)