cros: Add UMA metrics in migration UI to get more information from migration failures.

chrome/browser/ui/webui/chromeos/login/encryption_migration_screen_handler.h

 // Copyright 2017 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.
 
 #ifndef CHROME_BROWSER_UI_WEBUI_CHROMEOS_LOGIN_ENCRYPTION_MIGRATION_SCREEN_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_CHROMEOS_LOGIN_ENCRYPTION_MIGRATION_SCREEN_HANDLER_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 29 matching lines @@
   void SetShouldResume(bool should_resume) override;
   void SetContinueLoginCallback(ContinueLoginCallback callback) override;
   void SetupInitialView() override;
 
   // BaseScreenHandler implementation:
   void DeclareLocalizedValues(
       ::login::LocalizedValuesBuilder* builder) override;
   void Initialize() override;
 
  private:
-  // Enumeration for the migration state. These values must be kept in sync with
-  // EncryptionMigrationUIState in JS code.
+  // Enumeration for migration UI state. These values must be kept in sync with
+  // EncryptionMigrationUIState in JS code, and match the numbering for
+  // MigrationUIScreen in histograms/enums.xml. Do not reorder or remove items,
+  // only add new items before COUNT.
   enum UIState {
     INITIAL = 0,
     READY = 1,
     MIGRATING = 2,
     MIGRATION_FAILED = 3,
     NOT_ENOUGH_STORAGE = 4,
+    COUNT
   };
 
   // WebUIMessageHandler implementation:
   void RegisterMessages() override;
 
   // PowerManagerClient::Observer implementation:
   void PowerChanged(const power_manager::PowerSupplyProperties& proto) override;
 
   // Handlers for JS API callbacks.
   void HandleStartMigration();
   void HandleSkipMigration();
-  void HandleRequestRestart();
+  void HandleRequestRestartOnLowStorage();
+  void HandleRequestRestartOnFailure();
   void HandleOpenFeedbackDialog();
 
   // Updates UI state.
   void UpdateUIState(UIState state);
 
   void CheckAvailableStorage();
   void OnGetAvailableStorage(int64_t size);
   void WaitBatteryAndMigrate();
   void StartMigration();
   void OnMountExistingVault(bool success,
                             cryptohome::MountError return_code,
                             const std::string& mount_hash);
   void StartBlockingPowerSave();
   void StopBlockingPowerSave();
   // Removes cryptohome and shows the error screen after the removal finishes.
   void RemoveCryptohome();
   void OnRemoveCryptohome(bool success, cryptohome::MountError return_code);
 
   // Creates authorization key for MountEx method using |user_context_|.
   cryptohome::KeyDefinition GetAuthKey();
 
   // Handlers for cryptohome API callbacks.
   void OnMigrationProgress(cryptohome::DircryptoMigrationStatus status,
                            uint64_t current,
                            uint64_t total);
   void OnMigrationRequested(bool success);
 
+  // Records UMA about visible screen after delay.
+  void OnDelayedRecordVisibleScreen(UIState state);
+
   Delegate* delegate_ = nullptr;
   bool show_on_init_ = false;
 
   // The current UI state which should be refrected in the web UI.
   UIState current_ui_state_ = INITIAL;
 
   // The current user's UserContext, which is used to request the migration to
   // cryptohome.
   UserContext user_context_;
 
@@ skipping 18 matching lines @@
   std::unique_ptr<LoginFeedback> login_feedback_;
 
   base::WeakPtrFactory<EncryptionMigrationScreenHandler> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(EncryptionMigrationScreenHandler);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_UI_WEBUI_CHROMEOS_LOGIN_ENCRYPTION_MIGRATION_SCREEN_HANDLER_H_