Add a HostContentSettingsMap layer for Supervised Users.

components/content_settings/core/common/content_settings.h

Index: components/content_settings/core/common/content_settings.h
diff --git a/components/content_settings/core/common/content_settings.h b/components/content_settings/core/common/content_settings.h
index ae9fb93fdd38d0bc41281fbdf0bf4979df4fdedb..7f49a8c11d9fc217abb0211939f4b915d1923947 100644
--- a/components/content_settings/core/common/content_settings.h
+++ b/components/content_settings/core/common/content_settings.h
@@ -60,15 +60,16 @@ struct RendererContentSettingRules {
 namespace content_settings {
 
 // Enum containing the various source for content settings. Settings can be
-// set by policy, extension or the user. Certain (internal) schemes are
-// whilelisted. For whilelisted schemes the source is
-// |SETTING_SOURCE_WHITELIST|.
+// set by policy, extension, the user or by the custodian of a supervised user.
+// Certain (internal) schemes are whilelisted. For whilelisted schemes the
+// source is |SETTING_SOURCE_WHITELIST|.
 enum SettingSource {
   SETTING_SOURCE_NONE,
   SETTING_SOURCE_POLICY,
   SETTING_SOURCE_EXTENSION,
   SETTING_SOURCE_USER,
   SETTING_SOURCE_WHITELIST,
+  SETTING_SOURCE_SUPERVISED,
 };
 
 // |SettingInfo| provides meta data for content setting values. |source|