cros: Add UMA metrics in encryption migration UI.

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

 // 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.
 
 #include "chrome/browser/ui/webui/chromeos/login/encryption_migration_screen_handler.h"
 
+#include <cmath>
 #include <string>
 #include <utility>
 
 #include "ash/system/devicetype_utils.h"
 #include "base/command_line.h"
 #include "base/files/file_path.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/sys_info.h"
 #include "base/task_scheduler/post_task.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/lifetime/application_lifetime.h"
 #include "chrome/grit/generated_resources.h"
 #include "chromeos/chromeos_switches.h"
 #include "chromeos/cryptohome/async_method_caller.h"
 #include "chromeos/cryptohome/homedir_methods.h"
 #include "chromeos/dbus/cryptohome_client.h"
 #include "chromeos/dbus/dbus_thread_manager.h"
@@ skipping 16 matching lines @@
 constexpr int64_t kMinimumAvailableStorage = 10LL * 1024 * 1024;  // 10MB
 
 // The minimum battery level to start the migration.
 constexpr double kMinimumBatteryPercent = 30;
 
 // JS API callbacks names.
 constexpr char kJsApiStartMigration[] = "startMigration";
 constexpr char kJsApiSkipMigration[] = "skipMigration";
 constexpr char kJsApiRequestRestart[] = "requestRestart";
 
+// UMA names.
+constexpr char kUmaNameFirstScreen[] = "Cryptohome.MigrationUI.FirstScreen";
+constexpr char kUmaNameUserChoice[] = "Cryptohome.MigrationUI.UserChoice";
+constexpr char kUmaNameConsumedBatteryPercent[] =
+    "Cryptohome.MigrationUI.ConsumedBatteryPercent";
+
+// This enum must match the numbering for Cryptohome.MigrationUI.FirstScreen in
+// histograms.xml. Do not reorder or remove items, only add new items before
+// FIRST_SCREEN_MAX.
+enum FirstScreen {

[Ilya Sherman, 2017/04/28 21:07:52]

Optional nit: Mebbe use enum class here?

[fukino, 2017/04/29 14:40:31]

Done.

+  FIRST_SCREEN_READY = 0,
+  FIRST_SCREEN_RESUME = 1,
+  FIRST_SCREEN_LOW_STORAGE = 2,
+  FIRST_SCREEN_MAX

[Ilya Sherman, 2017/04/28 21:07:52]

Optional nit: Typically, "MAX" is used as an alias to the last item in the enum;
and "COUNT" is used to count the number of elements in the enum.  So, I'd rename
this to COUNT.

[fukino, 2017/04/29 14:40:31]

Agreed. Done.

+};
+
+// This enum must match the numbering for Cryptohome.MigrationUI.UserChoice in
+// histograms.xml. Do not reorder or remove items, only add new items before
+// FIRST_SCREEN_MAX.
+enum UserChoice {
+  USER_CHOICE_UPDATE = 0,
+  USER_CHOICE_SKIP = 1,
+  USER_CHOICE_MAX
+};
+
 bool IsTestingUI() {
   return base::CommandLine::ForCurrentProcess()->HasSwitch(
       chromeos::switches::kTestEncryptionMigrationUI);
 }
 
 }  // namespace
 
 namespace chromeos {
 
 EncryptionMigrationScreenHandler::EncryptionMigrationScreenHandler()
@@ skipping 121 matching lines @@
   // If the migration was already requested and the bettery level is enough now,
   // The migration should start immediately.
   if (current_battery_percent_ >= kMinimumBatteryPercent &&
       should_migrate_on_enough_battery_) {
     should_migrate_on_enough_battery_ = false;
     StartMigration();
   }
 }
 
 void EncryptionMigrationScreenHandler::HandleStartMigration() {
+  UMA_HISTOGRAM_ENUMERATION(kUmaNameUserChoice, USER_CHOICE_UPDATE,
+                            USER_CHOICE_MAX);
   WaitBatteryAndMigrate();
 }
 
 void EncryptionMigrationScreenHandler::HandleSkipMigration() {
+  UMA_HISTOGRAM_ENUMERATION(kUmaNameUserChoice, USER_CHOICE_SKIP,

[Ilya Sherman, 2017/04/28 21:07:51]

Please create a small wrapper function for recording metrics to this histogram. 
The UMA_HISTOGRAM macros expand to a nontrivial amount of code, so it's nice to
help the compiler avoid duplication of that code by wrapping it up in a single
call-site per histogram.

[fukino, 2017/04/29 14:40:31]

Done.

+                            USER_CHOICE_MAX);
   // If the user skips migration, we mount the cryptohome without performing the
   // migration by reusing UserContext and LoginPerformer which were used in the
   // previous attempt and dropping |is_forcing_dircrypto| flag in UserContext.
   // In this case, the user can not launch ARC apps in the session, and will be
   // asked to do the migration again in the next log-in attempt.
   if (!continue_login_callback_.is_null()) {
     user_context_.SetIsForcingDircrypto(false);
     std::move(continue_login_callback_).Run(user_context_);
   }
 }
@@ skipping 28 matching lines @@
           base::TaskPriority::USER_VISIBLE),
       base::Bind(&base::SysInfo::AmountOfFreeDiskSpace,
                  base::FilePath(kCheckStoragePath)),
       base::Bind(&EncryptionMigrationScreenHandler::OnGetAvailableStorage,
                  weak_ptr_factory_.GetWeakPtr()));
 }
 
 void EncryptionMigrationScreenHandler::OnGetAvailableStorage(int64_t size) {
   if (size >= kMinimumAvailableStorage || IsTestingUI()) {
     if (should_resume_) {
+      UMA_HISTOGRAM_ENUMERATION(kUmaNameFirstScreen, FIRST_SCREEN_RESUME,
+                                FIRST_SCREEN_MAX);
       WaitBatteryAndMigrate();
     } else {
+      UMA_HISTOGRAM_ENUMERATION(kUmaNameFirstScreen, FIRST_SCREEN_READY,
+                                FIRST_SCREEN_MAX);
       UpdateUIState(UIState::READY);
     }
   } else {
+    UMA_HISTOGRAM_ENUMERATION(kUmaNameFirstScreen, FIRST_SCREEN_LOW_STORAGE,
+                              FIRST_SCREEN_MAX);

[Ilya Sherman, 2017/04/28 21:07:52]

For this histogram, you could simply set the metric in the if/else branches, and
then log it at the bottom of this function.

[fukino, 2017/04/29 14:40:31]

I added a wrapper function for consistency with UserChoice.

     CallJS("setAvailableSpaceInString", ui::FormatBytes(size));
     CallJS("setNecessarySpaceInString",
            ui::FormatBytes(kMinimumAvailableStorage));
     UpdateUIState(UIState::NOT_ENOUGH_STORAGE);
   }
 }
 
 void EncryptionMigrationScreenHandler::WaitBatteryAndMigrate() {
   if (current_battery_percent_ >= kMinimumBatteryPercent) {
     StartMigration();
     return;
   }
   UpdateUIState(UIState::READY);
 
   should_migrate_on_enough_battery_ = true;
   DBusThreadManager::Get()->GetPowerManagerClient()->RequestStatusUpdate();
 }
 
 void EncryptionMigrationScreenHandler::StartMigration() {
   UpdateUIState(UIState::MIGRATING);
+  initial_battery_percent_ = current_battery_percent_;
 
   // Mount the existing eCryptfs vault to a temporary location for migration.
   cryptohome::MountParameters mount(false);
   mount.to_migrate_from_ecryptfs = true;
   cryptohome::HomedirMethods::GetInstance()->MountEx(
       cryptohome::Identification(user_context_.GetAccountId()),
       cryptohome::Authorization(GetAuthKey()), mount,
       base::Bind(&EncryptionMigrationScreenHandler::OnMountExistingVault,
                  weak_ptr_factory_.GetWeakPtr()));
 }
@@ skipping 78 matching lines @@
     uint64_t total) {
   switch (status) {
     case cryptohome::DIRCRYPTO_MIGRATION_INITIALIZING:
       UpdateUIState(UIState::MIGRATING);
       break;
     case cryptohome::DIRCRYPTO_MIGRATION_IN_PROGRESS:
       UpdateUIState(UIState::MIGRATING);
       CallJS("setMigrationProgress", static_cast<double>(current) / total);
       break;
     case cryptohome::DIRCRYPTO_MIGRATION_SUCCESS:
+      // If the battery level decreased during migration, record the consumed
+      // battery level.
+      if (current_battery_percent_ < initial_battery_percent_) {
+        UMA_HISTOGRAM_PERCENTAGE(
+            kUmaNameConsumedBatteryPercent,
+            static_cast<int>(std::round(initial_battery_percent_ -
+                                        current_battery_percent_)));
+      }
       // Restart immediately after successful migration.
       DBusThreadManager::Get()->GetPowerManagerClient()->RequestRestart();
       break;
     case cryptohome::DIRCRYPTO_MIGRATION_FAILED:
       // Stop listening to the progress updates.
       DBusThreadManager::Get()
           ->GetCryptohomeClient()
           ->SetDircryptoMigrationProgressHandler(
               CryptohomeClient::DircryptoMigrationProgessHandler());
       // Shows error screen after removing user directory is completed.
       RemoveCryptohome();
       break;
     default:
       break;
   }
 }
 
 void EncryptionMigrationScreenHandler::OnMigrationRequested(bool success) {
   LOG_IF(ERROR, !success) << "Requesting MigrateToDircrypto failed.";
   UpdateUIState(UIState::MIGRATION_FAILED);
 }
 
 }  // namespace chromeos