cros: Log authentication stage in LoginScreenController::OnShow.

There was one crash report in this method, but the crash did not seem to include
local variables. Log the value of authentication_stage_ to capture it.

Bug: 820671
Change-Id: I82c25b8a58f0993a9eef94c497c2c3e06c48b255
Reviewed-on: https://chromium-review.googlesource.com/1015880Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Jacob Dufault <jdufault@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553372}

ash/login/login_screen_controller.cc

@@ -11,6 +11,7 @@
 #include "ash/session/session_controller.h"
 #include "ash/shell.h"
 #include "ash/system/status_area_widget.h"
+#include "base/debug/alias.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chromeos/cryptohome/system_salt_getter.h"
@@ -87,7 +88,7 @@ void LoginScreenController::AuthenticateUser(const AccountId& account_id,
                                              OnAuthenticateCallback callback) {
   // It is an error to call this function while an authentication is in
   // progress.
-  LOG_IF(ERROR, authentication_stage_ == AuthenticationStage::kIdle)
+  LOG_IF(ERROR, authentication_stage_ != AuthenticationStage::kIdle)
       << "Authentication stage is " << static_cast<int>(authentication_stage_);
   CHECK_EQ(authentication_stage_, AuthenticationStage::kIdle);
 
@@ -420,7 +421,12 @@ LoginDataDispatcher* LoginScreenController::DataDispatcher() const {
 
 void LoginScreenController::OnShow() {
   SetSystemTrayVisibility(SystemTrayVisibility::kPrimary);
-  CHECK_EQ(authentication_stage_, AuthenticationStage::kIdle);
+  if (authentication_stage_ != AuthenticationStage::kIdle) {
+    AuthenticationStage authentication_stage = authentication_stage_;
+    base::debug::Alias(&authentication_stage);
+    LOG(FATAL) << "Unexpected authentication stage "
+               << static_cast<int>(authentication_stage_);
+  }
 }
 
 }  // namespace ash

ash/login/login_screen_controller.h

@@ -26,6 +26,14 @@ class LoginDataDispatcher;
 // LoginScreenClient through mojo.
 class ASH_EXPORT LoginScreenController : public mojom::LoginScreen {
  public:
+  // The current authentication stage. Used to get more verbose logging.
+  enum class AuthenticationStage {
+    kIdle,
+    kGetSystemSalt,
+    kDoAuthenticate,
+    kUserCallback,
+  };
+
   using OnShownCallback = base::OnceCallback<void(bool did_show)>;
   // Callback for authentication checks. |success| is nullopt if an
   // authentication check did not run, otherwise it is true/false if auth
@@ -113,6 +121,10 @@ class ASH_EXPORT LoginScreenController : public mojom::LoginScreen {
   // Flushes the mojo pipes - to be used in tests.
   void FlushForTesting();
 
+  AuthenticationStage authentication_stage() const {
+    return authentication_stage_;
+  }
+
  private:
   using PendingDoAuthenticateUser =
       base::OnceCallback<void(const std::string& system_salt)>;
@@ -136,13 +148,6 @@ class ASH_EXPORT LoginScreenController : public mojom::LoginScreen {
   // Bindings for users of the LockScreen interface.
   mojo::BindingSet<mojom::LoginScreen> bindings_;
 
-  // The current authentication stage. Used to get more verbose logging.
-  enum class AuthenticationStage {
-    kIdle,
-    kGetSystemSalt,
-    kDoAuthenticate,
-    kUserCallback,
-  };
   AuthenticationStage authentication_stage_ = AuthenticationStage::kIdle;
 
   base::ObserverList<LoginScreenControllerObserver> observers_;

ash/login/ui/lock_screen.cc

@@ -100,6 +100,14 @@ bool LockScreen::IsShown() {
 }
 
 void LockScreen::Destroy() {
+  LoginScreenController::AuthenticationStage authentication_stage =
+      ash::Shell::Get()->login_screen_controller()->authentication_stage();
+  base::debug::Alias(&authentication_stage);
+  if (ash::Shell::Get()->login_screen_controller()->authentication_stage() !=
+      authentication_stage) {
+    LOG(FATAL) << "Unexpected authentication stage "
+               << static_cast<int>(authentication_stage);
+  }
   CHECK_EQ(instance_, this);
 
   // Restore the initial wallpaper bluriness if they were changed.