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

components/content_settings/core/browser/website_settings_info.h

Index: components/content_settings/core/browser/website_settings_info.h
diff --git a/components/content_settings/core/browser/website_settings_info.h b/components/content_settings/core/browser/website_settings_info.h
index 762e32e828c4e52f58a802817d527fdb920a9297..bf146ee5d6a333edb1ae92353760012e499f91c3 100644
--- a/components/content_settings/core/browser/website_settings_info.h
+++ b/components/content_settings/core/browser/website_settings_info.h
@@ -50,6 +50,26 @@ class WebsiteSettingsInfo {
     DONT_INHERIT_IN_INCOGNITO,
   };
 
+  // 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 : uint32_t {

[raymes, 2016/05/25 03:36:07]

We could also have
typedef uint32_t Platforms; 
to make the function signatures more descriptive when we pass this around

[lshang, 2016/05/25 10:38:16]

Done.

+    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,
+  };

[raymes, 2016/05/25 03:36:07]

Hmm should we just have this is WebsiteSettingsRegistry since it's not used
here?

[lshang, 2016/05/25 10:38:16]

Done.

+
   WebsiteSettingsInfo(ContentSettingsType type,
                       const std::string& name,
                       std::unique_ptr<base::Value> initial_default_value,