Embedder and macOS embedding widely support metal (though its behind a gn flag). This issue tracks the remaining work items to make Metal the default rendering backend where supported on macOS.

• [macos] [metal] Support smooth resizing #74056
• Add support for external textures when rendering with metal on macos #73826
• [macos] [metal] Select rendering backend during engine start-up #74058

Prior to making an umbrella issue on 1/15/2020

Filing to track separately from #18208 since work will be needed to expose this though the embedding API. @chinmaygarde assigning to you since it seems like you're the best person to do this, having just done the Metal work for iOS and being very familiar with the embedding API, but let me know if that will be an issue.

I'm fine with turning Metal on by default for macOS immediately, which would be a way of getting a little bit more live testing of the Skia Metal backend before flipping the switch for iOS.