Improve the comments around content settings histograms.

components/content_settings/core/common/content_settings.cc

 // Copyright (c) 2011 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 "components/content_settings/core/common/content_settings.h"
 
 #include "base/containers/hash_tables.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/stl_util.h"
 #include "build/build_config.h"
 
 ContentSetting IntToContentSetting(int content_setting) {
   return ((content_setting < 0) ||
           (content_setting >= CONTENT_SETTING_NUM_SETTINGS)) ?
       CONTENT_SETTING_DEFAULT : static_cast<ContentSetting>(content_setting);
 }
 
 // WARNING: This array should not be reordered or removed as it is used for
-// histogram values. If a ContentSettingsType value has been removed, the entry
-// must be replaced by a placeholder. It should correspond directly to the
-// ContentType enum in histograms.xml.
+// histogram values. New content setting types must be added to the end.
+// If a ContentSettingsType value has been removed, the entry must be replaced
+// by a placeholder.
 // TODO(raymes): We should use a sparse histogram here on the hash of the
 // content settings type name instead.
 ContentSettingsType kHistogramOrder[] = {
     CONTENT_SETTINGS_TYPE_COOKIES,
     CONTENT_SETTINGS_TYPE_IMAGES,
     CONTENT_SETTINGS_TYPE_JAVASCRIPT,
     CONTENT_SETTINGS_TYPE_PLUGINS,
     CONTENT_SETTINGS_TYPE_POPUPS,
     CONTENT_SETTINGS_TYPE_GEOLOCATION,
     CONTENT_SETTINGS_TYPE_NOTIFICATIONS,
     CONTENT_SETTINGS_TYPE_AUTO_SELECT_CERTIFICATE,
     CONTENT_SETTINGS_TYPE_FULLSCREEN,
     CONTENT_SETTINGS_TYPE_MOUSELOCK,
     CONTENT_SETTINGS_TYPE_MIXEDSCRIPT,
     CONTENT_SETTINGS_TYPE_DEFAULT,  // MEDIASTREAM (removed).
     CONTENT_SETTINGS_TYPE_MEDIASTREAM_MIC,
     CONTENT_SETTINGS_TYPE_MEDIASTREAM_CAMERA,
     CONTENT_SETTINGS_TYPE_PROTOCOL_HANDLERS,
     CONTENT_SETTINGS_TYPE_PPAPI_BROKER,
     CONTENT_SETTINGS_TYPE_AUTOMATIC_DOWNLOADS,
     CONTENT_SETTINGS_TYPE_MIDI_SYSEX,
     CONTENT_SETTINGS_TYPE_PUSH_MESSAGING,
     CONTENT_SETTINGS_TYPE_SSL_CERT_DECISIONS,
-    CONTENT_SETTINGS_TYPE_DEFAULT,  // METRO_SWITCH_TO_DESKTOP (deprecated).
-#if defined(OS_ANDROID) || defined(OS_CHROMEOS)
+    CONTENT_SETTINGS_TYPE_DEFAULT,  // METRO_SWITCH_TO_DESKTOP (removed).
     CONTENT_SETTINGS_TYPE_PROTECTED_MEDIA_IDENTIFIER,
-#else
-    CONTENT_SETTINGS_TYPE_DEFAULT,  // PROTECTED_MEDIA_IDENTIFIER (mobile only).
-#endif
     CONTENT_SETTINGS_TYPE_APP_BANNER,
     CONTENT_SETTINGS_TYPE_SITE_ENGAGEMENT,
     CONTENT_SETTINGS_TYPE_DURABLE_STORAGE,
     CONTENT_SETTINGS_TYPE_KEYGEN,
     CONTENT_SETTINGS_TYPE_BLUETOOTH_GUARD,
     CONTENT_SETTINGS_TYPE_BACKGROUND_SYNC,
     CONTENT_SETTINGS_TYPE_AUTOPLAY,
 };
 
 int ContentSettingTypeToHistogramValue(ContentSettingsType content_setting,
@@ skipping 28 matching lines @@
 ContentSettingPatternSource::ContentSettingPatternSource()
     : setting(CONTENT_SETTING_DEFAULT), incognito(false) {
 }
 
 ContentSettingPatternSource::ContentSettingPatternSource(
     const ContentSettingPatternSource& other) = default;
 
 RendererContentSettingRules::RendererContentSettingRules() {}
 
 RendererContentSettingRules::~RendererContentSettingRules() {}