Remove support for the keygen tag

components/content_settings/core/browser/host_content_settings_map.h

Index: components/content_settings/core/browser/host_content_settings_map.h
diff --git a/components/content_settings/core/browser/host_content_settings_map.h b/components/content_settings/core/browser/host_content_settings_map.h
index e970af8c6c6ab6593d78cb5d184013b8508f416e..b74865acb39abbfc5c6760930572de5c19dc477e 100644
--- a/components/content_settings/core/browser/host_content_settings_map.h
+++ b/components/content_settings/core/browser/host_content_settings_map.h
@@ -314,7 +314,6 @@ class HostContentSettingsMap : public content_settings::Observer,
                            DomainToOriginMigrationStatus);
   FRIEND_TEST_ALL_PREFIXES(HostContentSettingsMapTest,
                            MigrateDomainScopedSettings);
-  FRIEND_TEST_ALL_PREFIXES(HostContentSettingsMapTest, MigrateKeygenSettings);
 
   friend class content_settings::TestUtils;
 
@@ -330,16 +329,6 @@ class HostContentSettingsMap : public content_settings::Observer,
       ContentSettingsType content_type,
       ProviderType* provider_type) const;
 
-  // Migrate Keygen settings which only use a primary pattern. Settings which
-  // only used a primary pattern were inconsistent in what they did with the
-  // secondary pattern. Some stored a ContentSettingsPattern::Wildcard() whereas
-  // others stored the same pattern twice. This function migrates all such
-  // settings to use ContentSettingsPattern::Wildcard(). This allows us to make
-  // the scoping code consistent across different settings.
-  // TODO(lshang): Remove this when clients have migrated (~M53). We should
-  // leave in some code to remove old-format settings for a long time.
-  void MigrateKeygenSettings();
-
   // Collect UMA data of exceptions.
   void RecordExceptionMetrics();