Fix Flutter Web not happy with FFI

@@ -21,10 +21,10 @@ import 'dart:typed_data';
 import 'package:flutter/rendering.dart' show Rect;
 import 'package:flutter/services.dart';
 import 'package:pdf/pdf.dart';
-import 'package:printing/src/method_channel_ffi.dart';
 
 import 'callback.dart';
 import 'interface.dart';
+import 'method_channel_ffi.dart' if (dart.library.js) 'method_channel_js.dart';
 import 'print_job.dart';
 import 'printer.dart';
 import 'printing_info.dart';

+/*
+ * Copyright (C) 2017, David PHAM-VAN <dev.nfet.net@gmail.com>
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import 'dart:typed_data';
+
+import 'print_job.dart';
+
+/// Set the Pdf document data
+void setDocumentFfi(PrintJob job, Uint8List data) {
+  throw UnimplementedError('Not using FFI');
+}
+
+/// Set the Pdf Error message
+void setErrorFfi(PrintJob job, String message) {
+  throw UnimplementedError('Not using FFI');
+}

@@ -27,13 +27,13 @@ import 'package:flutter/rendering.dart' show Rect;
 import 'package:flutter_web_plugins/flutter_web_plugins.dart';
 import 'package:image/image.dart' as im;
 import 'package:pdf/pdf.dart';
-import 'package:printing/src/pdfjs.dart';
-import 'package:printing/src/printer.dart';
-import 'package:printing/src/raster.dart';
 
 import 'callback.dart';
 import 'interface.dart';
+import 'pdfjs.dart';
+import 'printer.dart';
 import 'printing_info.dart';
+import 'raster.dart';
 
 /// Print plugin targetting Flutter on the Web
 class PrintingPlugin extends PrintingPlatform {