kiosk: UMA for launch error

chrome/browser/chromeos/app_mode/kiosk_app_launch_error.h

 // Copyright 2013 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_CHROMEOS_APP_MODE_KIOSK_APP_LAUNCH_ERROR_H_
 #define CHROME_BROWSER_CHROMEOS_APP_MODE_KIOSK_APP_LAUNCH_ERROR_H_
 
 #include <string>
 
 #include "base/macros.h"
 
 namespace chromeos {
 
+class AuthFailure;
+
 class KioskAppLaunchError {
  public:
+  // Enum used for UMA. Do NOT reorder or remove entry. Don't forget to
+  // update histograms.xml when adding new entries.
   enum Error {
-    NONE,                     // No error.
-    HAS_PENDING_LAUNCH,       // There is a pending launch already.
-    CRYPTOHOMED_NOT_RUNNING,  // Unable to call cryptohome daemon.
-    ALREADY_MOUNTED,          // Cryptohome is already mounted.
-    UNABLE_TO_MOUNT,          // Unable to mount cryptohome.
-    UNABLE_TO_REMOVE,         // Unable to remove cryptohome.
-    UNABLE_TO_INSTALL,        // Unable to install app.
-    USER_CANCEL,              // Canceled by user.
-    NOT_KIOSK_ENABLED,        // Not a kiosk enabled app.
-    UNABLE_TO_RETRIEVE_HASH,  // Unable to retrieve username hash.
-    POLICY_LOAD_FAILED,       // Failed to load policy for kiosk account.
-    UNABLE_TO_DOWNLOAD,       // Unable to download app's crx file.
-    UNABLE_TO_LAUNCH,         // Unable to launch app.
-    ARC_AUTH_FAILED,          // Failed to authorise ARC session
+    NONE = 0,                     // No error.
+    HAS_PENDING_LAUNCH = 1,       // There is a pending launch already.
+    CRYPTOHOMED_NOT_RUNNING = 2,  // Unable to call cryptohome daemon.
+    ALREADY_MOUNTED = 3,          // Cryptohome is already mounted.
+    UNABLE_TO_MOUNT = 4,          // Unable to mount cryptohome.
+    UNABLE_TO_REMOVE = 5,         // Unable to remove cryptohome.
+    UNABLE_TO_INSTALL = 6,        // Unable to install app.
+    USER_CANCEL = 7,              // Canceled by user.
+    NOT_KIOSK_ENABLED = 8,        // Not a kiosk enabled app.
+    UNABLE_TO_RETRIEVE_HASH = 9,  // Unable to retrieve username hash.
+    POLICY_LOAD_FAILED = 10,      // Failed to load policy for kiosk account.
+    UNABLE_TO_DOWNLOAD = 11,      // Unable to download app's crx file.
+    UNABLE_TO_LAUNCH = 12,        // Unable to launch app.
+    ARC_AUTH_FAILED = 13,         // Failed to authorise ARC session
+    ERROR_COUNT,                  // Count of all errors. Must be the last one.

[tbarzic, 2017/02/28 19:18:55]

I'd remove "Must be at least one" - there already is a comment not to remove
entries, so the fact ERROR_COUNT has to be >=1 is a moot point :)

[xiyuan, 2017/02/28 21:14:57]

Done.

   };
 
   // Returns a message for given |error|.
   static std::string GetErrorMessage(Error error);
 
-  // Save error for displaying on next restart. Note only the last saved error
-  // will be kept.
+  // Saves error for displaying and metric reporting on next chrome run.

[tbarzic, 2017/02/28 19:18:55]

nit: how about:
"Saves a launch error - used on the next Chrome run to report metrics and
display a message to the user."

[xiyuan, 2017/02/28 21:14:57]

Done.

+  // Note only the last saved error will be kept.
   static void Save(Error error);
 
+  // Saves cryptohome auth error for metric report on the next chrome run.
+  static void SaveCryptohomeFailure(const AuthFailure& auth_failure);
+
   // Gets the saved error.
   static Error Get();
 
-  // Clears the saved error.
-  static void Clear();
+  // Records the launch error metric and clears it.
+  static void RecordMetricAndClear();
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(KioskAppLaunchError);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_APP_MODE_KIOSK_APP_LAUNCH_ERROR_H_