Migrate old settings for ContentSettingTypes with wildcard as secondary_pattern

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 2308855ba577df3201d2054365ee6bec9394aec2..947e075b358dfbfd4718d04ae1e630aa9568fdcd 100644
--- a/components/content_settings/core/browser/host_content_settings_map.h
+++ b/components/content_settings/core/browser/host_content_settings_map.h
@@ -279,7 +279,8 @@ class HostContentSettingsMap : public content_settings::Observer,
 
  private:
   friend class base::RefCountedThreadSafe<HostContentSettingsMap>;
-  friend class HostContentSettingsMapTest_NonDefaultSettings_Test;
+  friend class HostContentSettingsMapTest_MigrateOldSettings_Test;
+
   friend class content_settings::TestUtils;
 
   typedef std::map<ProviderType, content_settings::ProviderInterface*>
@@ -293,6 +294,16 @@ class HostContentSettingsMap : public content_settings::Observer,
       ContentSettingsType content_type,
       content_settings::ProviderInterface* provider) const;
 
+  // Migrate old settings for those ContentSettingsType which previously
+  // would use the same pattern twice instead of using
+  // ContentSettingsPattern::Wildcard(). This has no impact on lookups using
+  // GetContentSetting (because Wildcard matches everything) but it has an
+  // impact when trying to change the existing content setting. We need to
+  // migrate the old-format keys.

[raymes, 2016/03/07 01:47:55]

I think we can rephrase this a bit because my explanation was probably not the
best :)

// Migrate old settings for ContentSettingsTypes 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.

[lshang, 2016/03/23 13:58:36]

Done.

+  // TODO(lshang): Remove this when clients have migrated. We should leave in
+  // some code to remove old-format settings for a long time.
+  void MigrateOldSettings();
+
   // Adds content settings for |content_type| and |resource_identifier|,
   // provided by |provider|, into |settings|. If |incognito| is true, adds only
   // the content settings which are applicable to the incognito mode and differ