Blur effect on cupertino controlls if GoogleMap is used

There's a weird interaction between this widget and the official [flutter google maps ](https://pub.dev/packages/google_maps_flutter).

Whenever the both widgets are in view the cupertino controls applies its backdrop filter .

I'm guessing this is the culprit, since if I remove sigmaX and sigmaY, the blur effect dissapears.
```dart
BackdropFilter(
filter: ui.ImageFilter.blur(
sigmaX: 10.0,
sigmaY: 10.0,
),
```
(line 132 in lib/src/cupertino_controls.dart)

I'm not sure if this is even in the scope of this package and maybe this should be posted in flutter's github, I'll include a sample code below the screenshot.


```dart
import 'dart:async';

import 'package:chewie/chewie.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';
import 'package:video_player/video_player.dart';

class Test extends StatefulWidget {
@override
_TestState createState() => _TestState();
}

class _TestState extends State {
VideoPlayerController _videoPlayerController;
ChewieController _chewieController;
final Completer _controller = Completer();

@override
void initState() {
_videoPlayerController =
VideoPlayerController.network('http://www.quintic.com/software/sample_videos/Football_Kick_Zoom.avi');

_chewieController = ChewieController(
videoPlayerController: _videoPlayerController,
aspectRatio: 16 / 9,
autoInitialize: true,
deviceOrientationsAfterFullScreen: [DeviceOrientation.portraitUp],
);

super.initState();
}

@override
void dispose() {
super.dispose();
}

@override
Widget build(BuildContext context) {
return Material(
color: Colors.white,
child: ListView(
children: [
SizedBox(
height: 500,
),
Chewie(
controller: _chewieController,
),
Container(
height: 400,
child: GoogleMap(
onMapCreated: (GoogleMapController controller) {
_controller.complete(controller);
},
initialCameraPosition: CameraPosition(
zoom: 2.0,
target: LatLng(35, 45),
),
),
)
],
),
);
}
}

```