Remove the migration code from content_settings::PrefProvider.

This is a follow-up to https://codereview.chromium.org/1252973002/. The situation is equivalent:
1. We expect most users to have been migrated from the old preferences, as the migration code has been live for 3 milestones.
2. We can remove the media and cookies migration code, as they are older and the deprecated values could not have made it to the new preferences.

TESTED=Effects on websites in the regular mode and incognito, syncing between two machines

BUG=452388

Review URL: https://codereview.chromium.org/1257093002

Cr-Commit-Position: refs/heads/master@{#341720}

6 files changed, 58 insertions, 582 deletions

diff --git a/components/content_settings/core/browser/content_settings_pref.cc b/components/content_settings/core/browser/content_settings_pref.cc
index a519cef..535bcc6 100644
--- a/components/content_settings/core/browser/content_settings_pref.cc
+++ b/components/content_settings/core/browser/content_settings_pref.cc
@@ -23,7 +23,6 @@ namespace {
 
 const char kSettingPath[] = "setting";
 const char kPerResourceIdentifierPrefName[] = "per_resource";
-const char kPerPluginPrefName[] = "per_plugin";
 const char kLastUsed[] = "last_used";
 
 ContentSetting FixObsoleteCookiePromptMode(ContentSettingsType content_type,
@@ -53,7 +52,6 @@ ContentSettingsPref::ContentSettingsPref(
     PrefChangeRegistrar* registrar,
     const char* pref_name,
     bool incognito,
-    bool* updating_old_preferences_flag,
     NotifyObserversCallback notify_callback)
     : content_type_(content_type),
       prefs_(prefs),
@@ -61,23 +59,10 @@ ContentSettingsPref::ContentSettingsPref(
       pref_name_(pref_name),
       is_incognito_(incognito),
       updating_preferences_(false),
-      updating_old_preferences_(updating_old_preferences_flag),
       notify_callback_(notify_callback) {
   DCHECK(prefs_);
 
-  // If the migration hasn't happened yet, or if this content setting
-  // is syncable, the parent |PrefProvider| is going to copy the contents
-  // of the old preference to this new preference. There is no need
-  // to initialize this preference separately (in fact, in the case
-  // of migration, we would be writing the empty new preference back to the
-  // old one, erasing it). Since copying between preferences is disallowed
-  // in incognito, |ContentSettingsPref| needs to be initialized from the new
-  // preference in incognito as well.
-  if ((prefs_->GetBoolean(prefs::kMigratedContentSettingsPatternPairs) &&
-       !IsContentSettingsTypeSyncable(content_type_))
-      || is_incognito_) {
-    ReadContentSettingsFromPrefAndWriteToOldPref();
-  }
+  ReadContentSettingsFromPref();
 
   registrar_->Add(
       pref_name_,
@@ -139,12 +124,6 @@ bool ContentSettingsPref::SetWebsiteSetting(
                secondary_pattern,
                resource_identifier,
                value.get());
-    if (IsContentSettingsTypeSyncable(content_type_)) {
-      UpdateOldPref(primary_pattern,
-                    secondary_pattern,
-                    resource_identifier,
-                    value.get());
-    }
   }
 
   notify_callback_.Run(
@@ -167,16 +146,13 @@ void ContentSettingsPref::ClearAllContentSettingsRules() {
   }
 
   if (!is_incognito_) {
-    // Clear the new preference.
+    // Clear the preference.
     {
       base::AutoReset<bool> auto_reset(&updating_preferences_, true);
       DictionaryPrefUpdate update(prefs_, pref_name_);
       base::DictionaryValue* pattern_pairs_settings = update.Get();
       pattern_pairs_settings->Clear();
     }
-
-    if (IsContentSettingsTypeSyncable(content_type_))
-      ClearOldPreference();
   }
 
   notify_callback_.Run(ContentSettingsPattern(),
@@ -249,14 +225,14 @@ size_t ContentSettingsPref::GetNumExceptions() {
   return value_map_.size();
 }
 
-void ContentSettingsPref::ReadContentSettingsFromPrefAndWriteToOldPref() {
-  // Clear the old preference, so we can copy the exceptions from the new
-  // preference into it. Note that copying in this direction is disallowed
-  // in incognito, to avoid the echo effect: New preference -> PrefProvider ->
-  // Old preference -> Incognito PrefProvider -> New preference -> etc.
-  if (!is_incognito_ && IsContentSettingsTypeSyncable(content_type_))
-    ClearOldPreference();
+bool ContentSettingsPref::TryLockForTesting() const {
+  if (!lock_.Try())
+    return false;
+  lock_.Release();
+  return true;
+}
 
+void ContentSettingsPref::ReadContentSettingsFromPref() {
   // |DictionaryPrefUpdate| sends out notifications when destructed. This
   // construction order ensures |AutoLock| gets destroyed first and |lock_| is
   // not held when the notifications are sent. Also, |auto_reset| must be still
@@ -328,12 +304,6 @@ void ContentSettingsPref::ReadContentSettingsFromPrefAndWriteToOldPref() {
                               content_type_,
                               resource_identifier,
                               setting_ptr->DeepCopy());
-          if (!is_incognito_ && IsContentSettingsTypeSyncable(content_type_)) {
-              UpdateOldPref(pattern_pair.first,
-                            pattern_pair.second,
-                            resource_identifier,
-                            setting_ptr.get());
-          }
         }
       }
     }
@@ -364,12 +334,6 @@ void ContentSettingsPref::ReadContentSettingsFromPrefAndWriteToOldPref() {
                           content_type_,
                           ResourceIdentifier(),
                           value->DeepCopy());
-      if (!is_incognito_ && IsContentSettingsTypeSyncable(content_type_)) {
-          UpdateOldPref(pattern_pair.first,
-                        pattern_pair.second,
-                        ResourceIdentifier(),
-                        value_ptr.get());
-      }
       if (content_type_ == CONTENT_SETTINGS_TYPE_COOKIES) {
         ContentSetting s = ValueToContentSetting(value);
         switch (s) {
@@ -407,7 +371,7 @@ void ContentSettingsPref::OnPrefChanged() {
   if (updating_preferences_)
     return;
 
-  ReadContentSettingsFromPrefAndWriteToOldPref();
+  ReadContentSettingsFromPref();
 
   notify_callback_.Run(ContentSettingsPattern(),
                        ContentSettingsPattern(),
@@ -486,127 +450,6 @@ void ContentSettingsPref::UpdatePref(
   }
 }
 
-void ContentSettingsPref::UpdateOldPref(
-    const ContentSettingsPattern& primary_pattern,
-    const ContentSettingsPattern& secondary_pattern,
-    const ResourceIdentifier& resource_identifier,
-    const base::Value* value) {
-  DCHECK(IsContentSettingsTypeSyncable(content_type_));
-
-  // The incognito provider cannot write the settings to avoid echo effect:
-  // New preference -> PrefProvider -> Old preference ->
-  // -> Incognito PrefProvider -> New preference -> etc.
-  DCHECK(!is_incognito_);
-
-  if (*updating_old_preferences_)
-    return;
-
-  base::AutoReset<bool> auto_reset(updating_old_preferences_, true);
-  {
-    DictionaryPrefUpdate update(prefs_,
-                                prefs::kContentSettingsPatternPairs);
-    base::DictionaryValue* pattern_pairs_settings = update.Get();
-
-    // Get settings dictionary for the given patterns.
-    std::string pattern_str(CreatePatternString(primary_pattern,
-                                                secondary_pattern));
-    base::DictionaryValue* settings_dictionary = NULL;
-    bool found = pattern_pairs_settings->GetDictionaryWithoutPathExpansion(
-        pattern_str, &settings_dictionary);
-
-    if (!found && value) {
-      settings_dictionary = new base::DictionaryValue;
-      pattern_pairs_settings->SetWithoutPathExpansion(
-          pattern_str, settings_dictionary);
-    }
-
-    if (settings_dictionary) {
-      if (content_type_ == CONTENT_SETTINGS_TYPE_PLUGINS &&
-          !resource_identifier.empty()) {
-        base::DictionaryValue* resource_dictionary = NULL;
-        found = settings_dictionary->GetDictionary(
-            kPerPluginPrefName, &resource_dictionary);
-        if (!found) {
-          if (value == NULL)
-            return;  // Nothing to remove. Exit early.
-          resource_dictionary = new base::DictionaryValue;
-          settings_dictionary->Set(kPerPluginPrefName, resource_dictionary);
-        }
-        // Update resource dictionary.
-        if (value == NULL) {
-          resource_dictionary->RemoveWithoutPathExpansion(resource_identifier,
-                                                          NULL);
-          if (resource_dictionary->empty()) {
-            settings_dictionary->RemoveWithoutPathExpansion(
-                kPerPluginPrefName, NULL);
-          }
-        } else {
-          resource_dictionary->SetWithoutPathExpansion(
-              resource_identifier, value->DeepCopy());
-        }
-      } else {
-        // Update settings dictionary.
-        std::string setting_path = GetTypeName(content_type_);
-        if (value == NULL) {
-          settings_dictionary->RemoveWithoutPathExpansion(setting_path,
-                                                          NULL);
-          settings_dictionary->RemoveWithoutPathExpansion(kLastUsed, NULL);
-        } else {
-          settings_dictionary->SetWithoutPathExpansion(
-              setting_path, value->DeepCopy());
-        }
-      }
-      // Remove the settings dictionary if it is empty.
-      if (settings_dictionary->empty()) {
-        pattern_pairs_settings->RemoveWithoutPathExpansion(
-            pattern_str, NULL);
-      }
-    }
-  }
-}
-
-void ContentSettingsPref::ClearOldPreference() {
-  DCHECK(IsContentSettingsTypeSyncable(content_type_));
-
-  if (*updating_old_preferences_)
-    return;
-
-  std::vector<std::string> keys;
-
-  base::AutoReset<bool> auto_reset(updating_old_preferences_, true);
-  DictionaryPrefUpdate update(prefs_, prefs::kContentSettingsPatternPairs);
-  base::DictionaryValue* old_dictionary = update.Get();
-
-  for (base::DictionaryValue::Iterator it(*old_dictionary);
-       !it.IsAtEnd(); it.Advance()) {
-    keys.push_back(it.key());
-  }
-
-  for (const std::string& key : keys) {
-    base::DictionaryValue* exception;
-    bool is_dictionary =
-        old_dictionary->GetDictionaryWithoutPathExpansion(key, &exception);
-    DCHECK(is_dictionary);
-
-    exception->RemoveWithoutPathExpansion(GetTypeName(content_type_), NULL);
-
-    base::DictionaryValue* last_used;
-    if (exception->GetDictionaryWithoutPathExpansion(kLastUsed, &last_used)) {
-      last_used->RemoveWithoutPathExpansion(GetTypeName(content_type_), NULL);
-
-      if (last_used->empty())
-        exception->RemoveWithoutPathExpansion(kLastUsed, NULL);
-    }
-
-    if (content_type_ == CONTENT_SETTINGS_TYPE_PLUGINS)
-      exception->RemoveWithoutPathExpansion(kPerPluginPrefName, NULL);
-
-    if (exception->empty())
-      old_dictionary->RemoveWithoutPathExpansion(key, NULL);
-  }
-
-}
-
 // static
 void ContentSettingsPref::CanonicalizeContentSettingsExceptions(
     base::DictionaryValue* all_settings_dictionary) {
diff --git a/components/content_settings/core/browser/content_settings_pref.h b/components/content_settings/core/browser/content_settings_pref.h
index 1314e16..2dd554b 100644
--- a/components/content_settings/core/browser/content_settings_pref.h
+++ b/components/content_settings/core/browser/content_settings_pref.h
@@ -45,7 +45,6 @@ class ContentSettingsPref {
                       PrefChangeRegistrar* registrar,
                       const char* pref_name,
                       bool incognito,
-                      bool* updating_old_preferences_flag,
                       NotifyObserversCallback notify_callback);
   ~ContentSettingsPref();
 
@@ -68,15 +67,17 @@ class ContentSettingsPref {
 
   size_t GetNumExceptions();
 
+  // Tries to lock |lock_|. If successful, returns true and releases the lock.
+  bool TryLockForTesting() const;
+
  private:
-  // Only to access static method CanonicalizeContentSettingsExceptions,
-  // so that we reduce duplicity between the two.
-  // TODO(msramek): Remove this after the migration is over.
-  friend class PrefProvider;
+  // TODO(msramek): Currently only needed in the unittest to get the
+  // corresponding pref name. Remove once pref names are in WebsiteSettingsInfo.
+  friend class DeadlockCheckerObserver;
 
-  // Reads all content settings exceptions from the preference and load them
+  // Reads all content settings exceptions from the preference and loads them
   // into the |value_map_|. The |value_map_| is cleared first.
-  void ReadContentSettingsFromPrefAndWriteToOldPref();
+  void ReadContentSettingsFromPref();
 
   // Callback for changes in the pref with the same name.
   void OnPrefChanged();
@@ -99,20 +100,6 @@ class ContentSettingsPref {
   // release it.
   void AssertLockNotHeld() const;
 
-  // Update the old aggregate preference, so that the settings can be synced
-  // to old versions of Chrome.
-  // TODO(msramek): Remove after the migration is over.
-  void UpdateOldPref(
-      const ContentSettingsPattern& primary_pattern,
-      const ContentSettingsPattern& secondary_pattern,
-      const ResourceIdentifier& resource_identifier,
-      const base::Value* value);
-
-  // Remove all exceptions of |content_type_| from the old aggregate dictionary
-  // preference.
-  // TODO(msramek): Remove after the migration is over.
-  void ClearOldPreference();
-
   // The type of content settings stored in this pref.
   ContentSettingsType content_type_;
 
@@ -131,11 +118,6 @@ class ContentSettingsPref {
   // notifications from the preferences service that we triggered ourself.
   bool updating_preferences_;
 
-  // Whether we are currently updating the old aggregate dictionary preference.
-  // Owned by the parent |PrefProvider| and shared by all its children
-  // |ContentSettingsPref|s.
-  bool* updating_old_preferences_;
-
   OriginIdentifierValueMap value_map_;
 
   OriginIdentifierValueMap incognito_value_map_;
diff --git a/components/content_settings/core/browser/content_settings_pref_provider.cc b/components/content_settings/core/browser/content_settings_pref_provider.cc
index ef80480..8e77612 100644
--- a/components/content_settings/core/browser/content_settings_pref_provider.cc
+++ b/components/content_settings/core/browser/content_settings_pref_provider.cc
@@ -30,40 +30,12 @@
 
 namespace {
 
-const char kPerPluginPrefName[] = "per_plugin";
-
-// Returns true and sets |pref_key| to the key in the content settings
-// dictionary under which per-resource content settings are stored,
-// if the given content type supports resource identifiers in user preferences.
-bool GetResourceTypeName(ContentSettingsType content_type,
-                         std::string* pref_key) {
-  if (content_type == CONTENT_SETTINGS_TYPE_PLUGINS) {
-    *pref_key = kPerPluginPrefName;
-    return true;
-  }
-  return false;
-}
-
-// TODO(msramek): Check if we still need this migration code. If not, remove it.
-ContentSetting FixObsoleteCookiePromptMode(ContentSettingsType content_type,
-                                           ContentSetting setting) {
-  if (content_type == CONTENT_SETTINGS_TYPE_COOKIES &&
-      setting == CONTENT_SETTING_ASK) {
-    return CONTENT_SETTING_BLOCK;
-  }
-  return setting;
-}
-
-// A helper function to duplicate |ContentSettingsPattern|, so that
-// |ReadContentSettingsFromOldPref| can export them in a vector. We cannot pass
-// them by pointer, because the original values will go out of scope when
-// the vector is used in |WriteSettingsToNewPreferences|.
-ContentSettingsPattern CopyPattern(const ContentSettingsPattern& pattern) {
-  return ContentSettingsPattern::FromString(pattern.ToString());
-}
-
-const char kAudioKey[] = "audio";
-const char kVideoKey[] = "video";
+// Obsolete prefs.
+// TODO(msramek): Remove the cleanup code after two releases (i.e. in M48).
+const char kObsoleteContentSettingsPatternPairs[] =
+    "profile.content_settings.pattern_pairs";
+const char kObsoleteMigratedContentSettingsPatternPairs[] =
+    "profile.migrated_content_settings_exceptions";
 
 // A list of exception preferences corresponding to individual content settings
 // types. Must be kept in sync with the enum |ContentSettingsType|.
@@ -116,29 +88,41 @@ void PrefProvider::RegisterProfilePrefs(
   registry->RegisterIntegerPref(
       prefs::kContentSettingsVersion,
       ContentSettingsPattern::kContentSettingsPatternVersion);
-  registry->RegisterDictionaryPref(
-      prefs::kContentSettingsPatternPairs,
-      user_prefs::PrefRegistrySyncable::SYNCABLE_PREF);
-  registry->RegisterBooleanPref(prefs::kMigratedContentSettingsPatternPairs,
-                                false);
 
   for (int i = 0; i < CONTENT_SETTINGS_NUM_TYPES; ++i) {
     registry->RegisterDictionaryPref(
         kContentSettingsExceptionsPrefs[i],
         PrefRegistrationFlagsForType(ContentSettingsType(i)));
   }
+
+  // Obsolete prefs ----------------------------------------------------------
+
+  registry->RegisterDictionaryPref(
+      kObsoleteContentSettingsPatternPairs,
+      user_prefs::PrefRegistrySyncable::SYNCABLE_PREF);
+  registry->RegisterBooleanPref(
+      kObsoleteMigratedContentSettingsPatternPairs, false);
+}
+
+// static
+bool PrefProvider::IsContentSettingsExceptionsPref(
+    const std::string& pref_name) {
+  for (const char* pref : kContentSettingsExceptionsPrefs) {
+    if (pref_name == pref)
+      return true;
+  }
+  return false;
 }
 
 PrefProvider::PrefProvider(PrefService* prefs, bool incognito)
     : prefs_(prefs),
       clock_(new base::DefaultClock()),
-      is_incognito_(incognito),
-      updating_old_preferences_(false) {
+      is_incognito_(incognito) {
   DCHECK(prefs_);
   // Verify preferences version.
   if (!prefs_->HasPrefPath(prefs::kContentSettingsVersion)) {
     prefs_->SetInteger(prefs::kContentSettingsVersion,
-                      ContentSettingsPattern::kContentSettingsPatternVersion);
+                       ContentSettingsPattern::kContentSettingsPatternVersion);
   }
   if (prefs_->GetInteger(prefs::kContentSettingsVersion) >
       ContentSettingsPattern::kContentSettingsPatternVersion) {
@@ -146,28 +130,11 @@ PrefProvider::PrefProvider(PrefService* prefs, bool incognito)
   }
 
   pref_change_registrar_.Init(prefs_);
-
-  pref_change_registrar_.Add(prefs::kContentSettingsPatternPairs, base::Bind(
-      &PrefProvider::OnOldContentSettingsPatternPairsChanged,
-      base::Unretained(this)));
-
   for (size_t i = 0; i < CONTENT_SETTINGS_NUM_TYPES; ++i) {
     content_settings_prefs_.push_back(new ContentSettingsPref(
         ContentSettingsType(i), prefs_, &pref_change_registrar_,
         kContentSettingsExceptionsPrefs[i], is_incognito_,
-        &updating_old_preferences_, base::Bind(&PrefProvider::Notify,
-                                               base::Unretained(this))));
-  }
-
-  // Migrate all the exceptions from the aggregate dictionary preference
-  // to the separate dictionaries, if this hasn't been done before.
-  if (!prefs_->GetBoolean(prefs::kMigratedContentSettingsPatternPairs)) {
-    WriteSettingsToNewPreferences(false);
-    prefs_->SetBoolean(prefs::kMigratedContentSettingsPatternPairs, true);
-  } else {
-    // Trigger the update of old preference, and as a result,
-    // the new preferences as well.
-    OnOldContentSettingsPatternPairsChanged();
+        base::Bind(&PrefProvider::Notify, base::Unretained(this))));
   }
 
   if (!is_incognito_) {
@@ -177,12 +144,9 @@ PrefProvider::PrefProvider(PrefService* prefs, bool incognito)
 
     UMA_HISTOGRAM_COUNTS("ContentSettings.NumberOfExceptions",
                          num_exceptions);
-
-    // Migrate the obsolete media content setting exceptions to the new
-    // settings.
-    MigrateObsoleteMediaContentSetting();
   }
 
+  DiscardObsoletePreferences();
 }
 
 PrefProvider::~PrefProvider() {
@@ -261,88 +225,6 @@ base::Time PrefProvider::GetLastUsage(
 // ////////////////////////////////////////////////////////////////////////////
 // Private
 
-PrefProvider::ContentSettingsPrefEntry::ContentSettingsPrefEntry(
-    const ContentSettingsPattern primary_pattern,
-    const ContentSettingsPattern secondary_pattern,
-    const ResourceIdentifier resource_identifier,
-    base::Value* value)
-    : primary_pattern(CopyPattern(primary_pattern)),
-      secondary_pattern(CopyPattern(secondary_pattern)),
-      resource_identifier(resource_identifier),
-      value(value) {
-}
-
-PrefProvider::ContentSettingsPrefEntry::ContentSettingsPrefEntry(
-    const ContentSettingsPrefEntry& entry)
-    : primary_pattern(CopyPattern(entry.primary_pattern)),
-      secondary_pattern(CopyPattern(entry.secondary_pattern)),
-      resource_identifier(entry.resource_identifier),
-      value(entry.value->DeepCopy()) {
-}
-
-PrefProvider::ContentSettingsPrefEntry&
-    PrefProvider::ContentSettingsPrefEntry::operator=(
-        const ContentSettingsPrefEntry& entry) {
-  this->primary_pattern = CopyPattern(entry.primary_pattern);
-  this->secondary_pattern = CopyPattern(entry.secondary_pattern);
-  this->resource_identifier = entry.resource_identifier;
-  this->value.reset(entry.value->DeepCopy());
-
-  return *this;
-}
-
-PrefProvider::ContentSettingsPrefEntry::~ContentSettingsPrefEntry() {}
-
-void PrefProvider::MigrateObsoleteMediaContentSetting() {
-  std::vector<Rule> rules_to_delete;
-  {
-    scoped_ptr<RuleIterator> rule_iterator(GetRuleIterator(
-        CONTENT_SETTINGS_TYPE_MEDIASTREAM, ResourceIdentifier(), false));
-    while (rule_iterator->HasNext()) {
-      // Skip default setting and rules without a value.
-      const content_settings::Rule& rule = rule_iterator->Next();
-      DCHECK(rule.primary_pattern != ContentSettingsPattern::Wildcard());
-      if (!rule.value.get())
-        continue;
-      rules_to_delete.push_back(rule);
-    }
-  }
-
-  for (std::vector<Rule>::const_iterator it = rules_to_delete.begin();
-       it != rules_to_delete.end(); ++it) {
-    const base::DictionaryValue* value_dict = NULL;
-    if (!it->value->GetAsDictionary(&value_dict) || value_dict->empty())
-      return;
-
-    std::string audio_device, video_device;
-    value_dict->GetString(kAudioKey, &audio_device);
-    value_dict->GetString(kVideoKey, &video_device);
-    // Add the exception to the new microphone content setting.
-    if (!audio_device.empty()) {
-      SetWebsiteSetting(it->primary_pattern,
-                        it->secondary_pattern,
-                        CONTENT_SETTINGS_TYPE_MEDIASTREAM_MIC,
-                        ResourceIdentifier(),
-                        new base::FundamentalValue(CONTENT_SETTING_ALLOW));
-    }
-    // Add the exception to the new camera content setting.
-    if (!video_device.empty()) {
-      SetWebsiteSetting(it->primary_pattern,
-                        it->secondary_pattern,
-                        CONTENT_SETTINGS_TYPE_MEDIASTREAM_CAMERA,
-                        ResourceIdentifier(),
-                        new base::FundamentalValue(CONTENT_SETTING_ALLOW));
-    }
-
-    // Remove the old exception in CONTENT_SETTINGS_TYPE_MEDIASTREAM.
-    SetWebsiteSetting(it->primary_pattern,
-                      it->secondary_pattern,
-                      CONTENT_SETTINGS_TYPE_MEDIASTREAM,
-                      ResourceIdentifier(),
-                      NULL);
-  }
-}
-
 void PrefProvider::Notify(
     const ContentSettingsPattern& primary_pattern,
     const ContentSettingsPattern& secondary_pattern,
@@ -354,180 +236,13 @@ void PrefProvider::Notify(
                   resource_identifier);
 }
 
-void PrefProvider::ReadContentSettingsFromOldPref() {
-  // |DictionaryPrefUpdate| sends out notifications when destructed. This
-  // construction order ensures |AutoLock| gets destroyed first and |old_lock_|
-  // is not held when the notifications are sent. Also, |auto_reset| must be
-  // still valid when the notifications are sent, so that |Observe| skips the
-  // notification.
-  base::AutoReset<bool> auto_reset(&updating_old_preferences_, true);
-  DictionaryPrefUpdate update(prefs_, prefs::kContentSettingsPatternPairs);
-
-  ClearPrefEntryMap();
-
-  const base::DictionaryValue* all_settings_dictionary =
-      prefs_->GetDictionary(prefs::kContentSettingsPatternPairs);
-
-  // Careful: The returned value could be NULL if the pref has never been set.
-  if (!all_settings_dictionary)
-    return;
-
-  base::DictionaryValue* mutable_settings;
-  scoped_ptr<base::DictionaryValue> mutable_settings_scope;
-
-  if (!is_incognito_) {
-    mutable_settings = update.Get();
-  } else {
-    // Create copy as we do not want to persist anything in OTR prefs.
-    mutable_settings = all_settings_dictionary->DeepCopy();
-    mutable_settings_scope.reset(mutable_settings);
-  }
-  // Convert all Unicode patterns into punycode form, then read.
-  ContentSettingsPref::CanonicalizeContentSettingsExceptions(mutable_settings);
-
-  for (base::DictionaryValue::Iterator i(*mutable_settings); !i.IsAtEnd();
-       i.Advance()) {
-    const std::string& pattern_str(i.key());
-    std::pair<ContentSettingsPattern, ContentSettingsPattern> pattern_pair =
-        ParsePatternString(pattern_str);
-    if (!pattern_pair.first.IsValid() ||
-        !pattern_pair.second.IsValid()) {
-      // TODO: Change this to DFATAL when crbug.com/132659 is fixed.
-      LOG(ERROR) << "Invalid pattern strings: " << pattern_str;
-      continue;
-    }
-
-    // Get settings dictionary for the current pattern string, and read
-    // settings from the dictionary.
-    const base::DictionaryValue* settings_dictionary = NULL;
-    bool is_dictionary = i.value().GetAsDictionary(&settings_dictionary);
-    DCHECK(is_dictionary);
-
-    for (size_t k = 0; k < CONTENT_SETTINGS_NUM_TYPES; ++k) {
-      ContentSettingsType content_type = static_cast<ContentSettingsType>(k);
-
-      std::string res_dictionary_path;
-      if (GetResourceTypeName(content_type, &res_dictionary_path)) {
-        const base::DictionaryValue* resource_dictionary = NULL;
-        if (settings_dictionary->GetDictionary(
-                res_dictionary_path, &resource_dictionary)) {
-          for (base::DictionaryValue::Iterator j(*resource_dictionary);
-               !j.IsAtEnd();
-               j.Advance()) {
-            const std::string& resource_identifier(j.key());
-            int setting = CONTENT_SETTING_DEFAULT;
-            bool is_integer = j.value().GetAsInteger(&setting);
-            DCHECK(is_integer);
-            DCHECK_NE(CONTENT_SETTING_DEFAULT, setting);
-
-            pref_entry_map_[content_type].push_back(
-                new ContentSettingsPrefEntry(
-                    pattern_pair.first,
-                    pattern_pair.second,
-                    resource_identifier,
-                    new base::FundamentalValue(setting)));
-          }
-        }
-      }
-      base::Value* value = NULL;
-      if (HostContentSettingsMap::ContentTypeHasCompoundValue(content_type)) {
-        const base::DictionaryValue* setting = NULL;
-        // TODO(xians): Handle the non-dictionary types.
-        if (settings_dictionary->GetDictionaryWithoutPathExpansion(
-            GetTypeName(content_type), &setting)) {
-          DCHECK(!setting->empty());
-          value = setting->DeepCopy();
-        }
-      } else {
-        int setting = CONTENT_SETTING_DEFAULT;
-        if (settings_dictionary->GetIntegerWithoutPathExpansion(
-                GetTypeName(content_type), &setting)) {
-          DCHECK_NE(CONTENT_SETTING_DEFAULT, setting);
-          setting = FixObsoleteCookiePromptMode(content_type,
-                                                ContentSetting(setting));
-          value = new base::FundamentalValue(setting);
-        }
-      }
-
-      // |pref_entry_map_| will take the ownership of |value|.
-      if (value != NULL) {
-        pref_entry_map_[content_type].push_back(
-            new ContentSettingsPrefEntry(
-                pattern_pair.first,
-                pattern_pair.second,
-                ResourceIdentifier(),
-                value));
-      }
-    }
-  }
-}
-
-void PrefProvider::WriteSettingsToNewPreferences(bool syncable_only) {
-  // The incognito provider cannot write the settings to avoid echo effect:
-  // New preference -> PrefProvider -> Old preference ->
-  // -> Incognito PrefProvider -> New preference -> etc.
-  if (is_incognito_)
-    return;
-
-  if (updating_old_preferences_)
-    return;
-
-  base::AutoReset<bool> auto_reset(&updating_old_preferences_, true);
-  base::AutoLock auto_lock(old_lock_);
-
-  ReadContentSettingsFromOldPref();
-
-  for (int k = 0; k < CONTENT_SETTINGS_NUM_TYPES; ++k) {
-    ContentSettingsType content_type = ContentSettingsType(k);
-
-    if (syncable_only && !IsContentSettingsTypeSyncable(content_type))
-      continue;
-
-    content_settings_prefs_[content_type]->ClearAllContentSettingsRules();
-
-    for (size_t i = 0; i < pref_entry_map_[content_type].size(); ++i) {
-#if defined(OS_CHROMEOS) || defined(OS_ANDROID)
-      // Protected Media Identifier "Allow" exceptions can not be migrated.
-      const base::FundamentalValue allow_value(CONTENT_SETTING_ALLOW);
-      if (content_type == CONTENT_SETTINGS_TYPE_PROTECTED_MEDIA_IDENTIFIER &&
-          pref_entry_map_[content_type][i]->value->Equals(&allow_value)) {
-        continue;
-      }
-#endif
-
-      content_settings_prefs_[content_type]->SetWebsiteSetting(
-          pref_entry_map_[content_type][i]->primary_pattern,
-          pref_entry_map_[content_type][i]->secondary_pattern,
-          pref_entry_map_[content_type][i]->resource_identifier,
-          pref_entry_map_[content_type][i]->value.release());
-    }
-  }
-
-  ClearPrefEntryMap();
-}
-
-void PrefProvider::ClearPrefEntryMap() {
-  for (int i = 0; i < CONTENT_SETTINGS_NUM_TYPES; ++i)
-    pref_entry_map_[i].clear();
-}
-
-void PrefProvider::OnOldContentSettingsPatternPairsChanged() {
-  DCHECK(thread_checker_.CalledOnValidThread());
-
-  WriteSettingsToNewPreferences(true);
-}
-
 void PrefProvider::SetClockForTesting(scoped_ptr<base::Clock> clock) {
   clock_ = clock.Pass();
 }
 
-bool PrefProvider::TestAllLocks() const {
-  for (size_t i = 0; i < CONTENT_SETTINGS_NUM_TYPES; ++i) {
-    if (!content_settings_prefs_[i]->lock_.Try())
-      return false;
-    content_settings_prefs_[i]->lock_.Release();
-  }
-  return true;
+void PrefProvider::DiscardObsoletePreferences() {
+  prefs_->ClearPref(kObsoleteContentSettingsPatternPairs);
+  prefs_->ClearPref(kObsoleteMigratedContentSettingsPatternPairs);
 }
 
 }  // namespace content_settings
diff --git a/components/content_settings/core/browser/content_settings_pref_provider.h b/components/content_settings/core/browser/content_settings_pref_provider.h
index ec235a9..7a64603 100644
--- a/components/content_settings/core/browser/content_settings_pref_provider.h
+++ b/components/content_settings/core/browser/content_settings_pref_provider.h
@@ -39,6 +39,10 @@ class PrefProvider : public ObservableProvider {
   PrefProvider(PrefService* prefs, bool incognito);
   ~PrefProvider() override;
 
+  // Whether |pref_name| is a name of one of the preferences for content
+  // settings exceptions.
+  static bool IsContentSettingsExceptionsPref(const std::string& pref_name);
+
   // ProviderInterface implementations.
   RuleIterator* GetRuleIterator(ContentSettingsType content_type,
                                 const ResourceIdentifier& resource_identifier,
@@ -72,18 +76,10 @@ class PrefProvider : public ObservableProvider {
   void SetClockForTesting(scoped_ptr<base::Clock> clock);
 
  private:
-  friend class DeadlockCheckerThread;  // For testing.
-
-  // Migrate the old media setting into new mic/camera content settings.
-  void MigrateObsoleteMediaContentSetting();
+  friend class DeadlockCheckerObserver;  // For testing.
 
-  // Migrate the settings from the old aggregate dictionary into the new format.
-  void MigrateAllExceptions();
-
-  // Writes the contents of the old aggregate dictionary preferences into
-  // separate dictionaries for content types. If |syncable_only| is true,
-  // only syncable content types will be written.
-  void WriteSettingsToNewPreferences(bool syncable_only);
+  // Clean up the obsolete preferences from the user's profile.
+  void DiscardObsoletePreferences();
 
   // Weak; owned by the Profile and reset in ShutdownOnUIThread.
   PrefService* prefs_;
@@ -97,54 +93,9 @@ class PrefProvider : public ObservableProvider {
 
   ScopedVector<ContentSettingsPref> content_settings_prefs_;
 
-  DISALLOW_COPY_AND_ASSIGN(PrefProvider);
-
-  bool TestAllLocks() const;
-
-  // All functionality regarding reading and writing of preferences has been
-  // moved to |ContentSettingsPref|, which manages one content type per
-  // instance. However, for backward compatibility, we need to be able to write
-  // to the old and deprecated aggregate dictionary preference which maintains
-  // all content types. Therefore, |ContentSettingsPrefProvider| must still
-  // retain some of the functionality of |ContentSettingsPref|. The following
-  // attributes and methods serve this purpose.
-  // TODO(msramek): Remove this migration code after two stable releases.
-  struct ContentSettingsPrefEntry {
-    ContentSettingsPrefEntry(const ContentSettingsPattern primary_pattern,
-                             const ContentSettingsPattern secondary_pattern,
-                             const ResourceIdentifier resource_identifier,
-                             base::Value* value);
-    ContentSettingsPrefEntry(const ContentSettingsPrefEntry& entry);
-    ContentSettingsPrefEntry& operator=(const ContentSettingsPrefEntry& entry);
-    ~ContentSettingsPrefEntry();
-
-    ContentSettingsPattern primary_pattern;
-    ContentSettingsPattern secondary_pattern;
-    ResourceIdentifier resource_identifier;
-    scoped_ptr<base::Value> value;
-  };
-
-  // Stores exceptions read from the old preference before writing them
-  // to the new one.
-  ScopedVector<ContentSettingsPrefEntry>
-      pref_entry_map_[CONTENT_SETTINGS_NUM_TYPES];
-
-  // Clears |pref_entry_map_|.
-  void ClearPrefEntryMap();
-
-  // Guards access to |pref_entry_map_|.
-  mutable base::Lock old_lock_;
-
-  // Indicates whether the old preferences are updated.
-  bool updating_old_preferences_;
-
-  // Called when the old preference changes.
-  void OnOldContentSettingsPatternPairsChanged();
-
-  // Reads the old preference and writes it to |pref_entry_map_|.
-  void ReadContentSettingsFromOldPref();
-
   base::ThreadChecker thread_checker_;
+
+  DISALLOW_COPY_AND_ASSIGN(PrefProvider);
 };
 
 }  // namespace content_settings
diff --git a/components/content_settings/core/common/pref_names.cc b/components/content_settings/core/common/pref_names.cc
index 4c0ffb2..0bf3013 100644
--- a/components/content_settings/core/common/pref_names.cc
+++ b/components/content_settings/core/common/pref_names.cc
@@ -13,12 +13,6 @@ const char kBlockThirdPartyCookies[] = "profile.block_third_party_cookies";
 // Version of the pattern format used to define content settings.
 const char kContentSettingsVersion[] = "profile.content_settings.pref_version";
 
-// Patterns for mapping origins to origin related settings. Default settings
-// will be applied to origins that don't match any of the patterns. The pattern
-// format used is defined by kContentSettingsVersion.
-const char kContentSettingsPatternPairs[] =
-    "profile.content_settings.pattern_pairs";
-
 // Integer that specifies the index of the tab the user was on when they
 // last visited the content settings window.
 const char kContentSettingsWindowLastTabIndex[] =
@@ -139,12 +133,6 @@ const char kContentSettingsSiteEngagementPatternPairs[] =
 const char kContentSettingsDurableStoragePatternPairs[] =
     "profile.content_settings.exceptions.durable_storage";
 
-// Whether the patern pairs have been migrated from the deprecated aggregate
-// preference |kContentSettingsPatternPairs| to the separate preferences
-// |kContentSettings<type>PatternPairs|.
-const char kMigratedContentSettingsPatternPairs[] =
-    "profile.migrated_content_settings_exceptions";
-
 // Preferences that are exclusively used to store managed values for default
 // content settings.
 const char kManagedDefaultCookiesSetting[] =
diff --git a/components/content_settings/core/common/pref_names.h b/components/content_settings/core/common/pref_names.h
index c7ee72d..ba3862c 100644
--- a/components/content_settings/core/common/pref_names.h
+++ b/components/content_settings/core/common/pref_names.h
@@ -11,7 +11,6 @@ namespace prefs {
 
 extern const char kBlockThirdPartyCookies[];
 extern const char kContentSettingsVersion[];
-extern const char kContentSettingsPatternPairs[];
 extern const char kContentSettingsWindowLastTabIndex[];
 
 extern const char kDefaultCookiesSetting[];
@@ -75,8 +74,6 @@ extern const char kContentSettingsAppBannerPatternPairs[];
 extern const char kContentSettingsSiteEngagementPatternPairs[];
 extern const char kContentSettingsDurableStoragePatternPairs[];
 
-extern const char kMigratedContentSettingsPatternPairs[];
-
 extern const char kManagedDefaultCookiesSetting[];
 extern const char kManagedDefaultImagesSetting[];
 extern const char kManagedDefaultJavaScriptSetting[];