Translate: Fix broken UMA entries

chrome/browser/translate/translate_browser_metrics.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_TRANSLATE_TRANSLATE_BROWSER_METRICS_H_
 #define CHROME_BROWSER_TRANSLATE_TRANSLATE_BROWSER_METRICS_H_
 
 #include <string>
 
 namespace TranslateBrowserMetrics {
 
 // An indexing type to query each UMA entry name via GetMetricsName() function.
 // Note: |kMetricsEntries| should be updated when a new entry is added here.
 enum MetricsNameIndex {
   UMA_INITIATION_STATUS,
   UMA_LANGUAGE_DETECTION_ERROR,
   UMA_LOCALES_ON_DISABLED_BY_PREFS,
   UMA_UNDISPLAYABLE_LANGUAGE,
   UMA_UNSUPPORTED_LANGUAGE_AT_INITIATION,
   UMA_MAX,
 };
 
 // When Chrome Translate is ready to translate a page, one of following reason
 // decide the next browser action.
+// Note: Don't insert any item. It will change reporting UMA value, and break
+// the UMA dashboard page. Insteads, append it at the end of enum as suggested
+// below.
 enum InitiationStatusType {
   INITIATION_STATUS_DISABLED_BY_PREFS,
   INITIATION_STATUS_DISABLED_BY_SWITCH,
   INITIATION_STATUS_DISABLED_BY_CONFIG,
   INITIATION_STATUS_LANGUAGE_IS_NOT_SUPPORTED,
-  INITIATION_STATUS_MIME_TYPE_IS_NOT_SUPPORTED,
   INITIATION_STATUS_URL_IS_NOT_SUPPORTED,
   INITIATION_STATUS_SIMILAR_LANGUAGES,
   INITIATION_STATUS_ACCEPT_LANGUAGES,
-
   INITIATION_STATUS_AUTO_BY_CONFIG,
   INITIATION_STATUS_AUTO_BY_LINK,
   INITIATION_STATUS_SHOW_INFOBAR,
-
+  INITIATION_STATUS_MIME_TYPE_IS_NOT_SUPPORTED,
+  // Insert new items here.
   INITIATION_STATUS_MAX,
 };
 
 // Called when Chrome Translate is initiated to report a reason of the next
 // browser action.
 void ReportInitiationStatus(InitiationStatusType type);
 
 // Called when Chrome opens the URL so that the user sends an error feedback.
 void ReportLanguageDetectionError();
 
 void ReportLocalesOnDisabledByPrefs(const std::string& locale);
 
 // Called when Chrome Translate server sends the language list which includes
 // a undisplayable language in the user's locale.
 void ReportUndisplayableLanguage(const std::string& language);
 
 void ReportUnsupportedLanguageAtInitiation(const std::string& language);
 
 // Provides UMA entry names for unit tests.
 const char* GetMetricsName(MetricsNameIndex index);
 
 }  // namespace TranslateBrowserMetrics
 
 #endif  // CHROME_BROWSER_TRANSLATE_TRANSLATE_BROWSER_METRICS_H_