forked from firka/flutter
This PR moves the source of truth for`devicePixelRatio` to the `EngineFlutterDisplay` singleton. Main things that this PR is trying to do: - `EngineFlutterDisplay` is a singleton that represents information about the display. - The `devicePixelRatio` can be overriden in tests. - The `browserDevicePixelRatio` gets the value directly from the browser and can't be overriden. - Remove `EngineSingletonFlutterWindow` and incorporate it into `EngineFlutterWindow`.