Remove dependency to dart:io

@@ -26,9 +26,9 @@ import 'package:meta/meta.dart';
 import 'package:utf/utf.dart';
 import 'package:vector_math/vector_math_64.dart';
 
-import 'src/io.dart'
-    if (dart.library.io) 'src/io_vm.dart'
-    if (dart.library.js) 'src/io_archive.dart';
+import 'io/interface.dart'
+    if (dart.library.io) 'io/vm.dart'
+    if (dart.library.js) 'io/js.dart';
 
 part 'src/annotation.dart';
 part 'src/array.dart';

@@ -16,6 +16,5 @@ dependencies:
   crypto: "^2.0.6"
   archive: "^2.0.10"
 
-
 dev_dependencies:
   test: any

@@ -17,7 +17,6 @@
 library printing;
 
 import 'dart:async';
-import 'dart:io';
 import 'dart:typed_data';
 import 'dart:ui' as ui;
 

@@ -107,9 +107,6 @@ mixin Printing {
 
   /// Opens the native printer picker interface, and returns the URL of the selected printer.
   static Future<Printer> pickPrinter({Rect bounds}) async {
-    if (!Platform.isIOS) {
-      return null;
-    }
     _channel.setMethodCallHandler(_handleMethod);
     bounds ??= Rect.fromCircle(center: Offset.zero, radius: 10);
     final Map<String, dynamic> params = <String, dynamic>{
@@ -142,9 +139,6 @@ mixin Printing {
     @required LayoutCallback onLayout,
     String name = 'Document',
   }) async {
-    if (!Platform.isIOS || printer == null) {
-      return false;
-    }
     _onCompleted = Completer<bool>();
     _channel.setMethodCallHandler(_handleMethod);
     final List<int> bytes = await onLayout(PdfPageFormat.standard);