Add 'autoplay' content settings and expose it to Blink.

components/content_settings/core/browser/content_settings_registry.cc

Index: components/content_settings/core/browser/content_settings_registry.cc
diff --git a/components/content_settings/core/browser/content_settings_registry.cc b/components/content_settings/core/browser/content_settings_registry.cc
index 9c66ce35e919c8408d78ab6480a839dcc8e1c523..6aa85d0e1e266eda72f461cfa40a674283b5577d 100644
--- a/components/content_settings/core/browser/content_settings_registry.cc
+++ b/components/content_settings/core/browser/content_settings_registry.cc
@@ -271,6 +271,13 @@ void ContentSettingsRegistry::Init() {
            WebsiteSettingsInfo::REQUESTING_ORIGIN_ONLY_SCOPE,
            ContentSettingsInfo::INHERIT_IN_INCOGNITO);
 
+  Register(CONTENT_SETTINGS_TYPE_AUTOPLAY, "autoplay",
+           CONTENT_SETTING_ALLOW, WebsiteSettingsInfo::UNSYNCABLE,
+           WhitelistedSchemes(),
+           ValidSettings(CONTENT_SETTING_ALLOW, CONTENT_SETTING_BLOCK),
+           WebsiteSettingsInfo::REQUESTING_ORIGIN_ONLY_SCOPE,
+           ContentSettingsInfo::INHERIT_IN_INCOGNITO);
+
   // Content settings that aren't used to store any data. TODO(raymes): use a
   // different mechanism rather than content settings to represent these.
   // Since nothing is stored in them, there is no real point in them being a