Only Register() platform specific content settings types on different platforms

components/content_settings/core/browser/website_settings_registry.h

Index: components/content_settings/core/browser/website_settings_registry.h
diff --git a/components/content_settings/core/browser/website_settings_registry.h b/components/content_settings/core/browser/website_settings_registry.h
index a10f1b08ceeaa310e68626ae19500df312e27bc9..1f4ec47e9e4a9cc8b5cefda00fe65feed9c5b21d 100644
--- a/components/content_settings/core/browser/website_settings_registry.h
+++ b/components/content_settings/core/browser/website_settings_registry.h
@@ -25,6 +25,27 @@ namespace content_settings {
 // const.
 class WebsiteSettingsRegistry {
  public:
+  typedef uint32_t Platforms;
+  // TODO(lshang): Remove this enum when content settings can be registered from
+  // within the component in which they are used. When this is possible then
+  // ifdefs can be contained within each component.
+  enum Platform : Platforms {
+    PLATFORM_WINDOWS = 1 << 0,
+    PLATFORM_LINUX = 1 << 1,
+    PLATFORM_CHROMEOS = 1 << 2,
+    PLATFORM_MAC = 1 << 3,
+    PLATFORM_ANDROID = 1 << 4,
+    PLATFORM_IOS = 1 << 5,
+
+    // Settings only applied to win, mac, linux and chromeos.
+    DESKTOP =
+        PLATFORM_WINDOWS | PLATFORM_LINUX | PLATFORM_CHROMEOS | PLATFORM_MAC,
+
+    // Settings applied to all platforms, including win, mac, linux, chromeos,
+    // android, ios.
+    ALL_PLATFORMS = DESKTOP | PLATFORM_ANDROID | PLATFORM_IOS,
+  };
+
   using Map =
       std::map<ContentSettingsType, std::unique_ptr<WebsiteSettingsInfo>>;
   using const_iterator = MapValueIterator<typename Map::const_iterator,
@@ -41,6 +62,8 @@ class WebsiteSettingsRegistry {
   // Register a new website setting. This maps an origin to an arbitrary
   // base::Value. Returns a pointer to the registered WebsiteSettingsInfo which
   // is owned by the registry.
+  // A nullptr will be returned if registration fails (for example if
+  // |platforms| doesn't match the current platform).
   const WebsiteSettingsInfo* Register(
       ContentSettingsType type,
       const std::string& name,
@@ -48,6 +71,7 @@ class WebsiteSettingsRegistry {
       WebsiteSettingsInfo::SyncStatus sync_status,
       WebsiteSettingsInfo::LossyStatus lossy_status,
       WebsiteSettingsInfo::ScopingType scoping_type,
+      Platforms platforms,
       WebsiteSettingsInfo::IncognitoBehavior incognito_behavior);
 
   const_iterator begin() const;