Sync clients should be able to handle device-specific URL schemes

[diracdeltas]

Some URL schemes do not work cross-platform. Ex:

browser-laptop: chrome:, chrome-extension:, about: (?) android: chrome-native: (?) ios: ?

When these URLs are synced as a bookmark or history record, a receiver which is not able to handle the URL scheme should either hide the record or show some kind of warning to the user.

cc @SergeyZhukovsky @jhreis