feat: add optional headers param to network image (#13128)

* feat: add optional headers params to network image

* fix: addressed comments

* feat: add test

* style: format code

packages/flutter/lib/src/services/image_provider.dart

@@ -401,7 +401,7 @@ class NetworkImage extends ImageProvider<NetworkImage> {
   /// Creates an object that fetches the image at the given URL.
   ///
   /// The arguments must not be null.
-  const NetworkImage(this.url, { this.scale: 1.0 })
+  const NetworkImage(this.url, { this.scale: 1.0 , this.headers })
       : assert(url != null),
         assert(scale != null);
 
@@ -411,6 +411,9 @@ class NetworkImage extends ImageProvider<NetworkImage> {
   /// The scale to place in the [ImageInfo] object of the image.
   final double scale;
 
+  /// The HTTP headers that will be used with [HttpClient.get] to fetch image from network.
+  final Map<String, String> headers;
+
   @override
   Future<NetworkImage> obtainKey(ImageConfiguration configuration) {
     return new SynchronousFuture<NetworkImage>(this);
@@ -434,7 +437,7 @@ class NetworkImage extends ImageProvider<NetworkImage> {
     assert(key == this);
 
     final Uri resolved = Uri.base.resolve(key.url);
-    final http.Response response = await _httpClient.get(resolved);
+    final http.Response response = await _httpClient.get(resolved, headers: headers);
     if (response == null || response.statusCode != 200)
       throw new Exception('HTTP request failed, statusCode: ${response?.statusCode}, $resolved');
 

packages/flutter/lib/src/widgets/image.dart

@@ -129,6 +129,7 @@ class Image extends StatefulWidget {
   /// Creates a widget that displays an [ImageStream] obtained from the network.
   ///
   /// The [src], [scale], and [repeat] arguments must not be null.
+  /// An optional [headers] argument can be used to use custom HTTP headers.
   ///
   /// All network images are cached regardless of HTTP headers.
   Image.network(String src, {
@@ -145,7 +146,8 @@ class Image extends StatefulWidget {
     this.matchTextDirection: false,
     this.gaplessPlayback: false,
     this.package,
-  }) : image = new NetworkImage(src, scale: scale),
+    Map<String, String> headers,
+  }) : image = new NetworkImage(src, scale: scale, headers: headers),
        assert(alignment != null),
        assert(repeat != null),
        assert(matchTextDirection != null),

packages/flutter/test/widgets/image_headers_test.dart

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:async';
+import 'package:flutter/services.dart';
+import 'package:flutter/widgets.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:http/http.dart' as http;
+import 'package:http/testing.dart' as http;
+import 'package:flutter/services.dart' show createHttpClient;
+
+import '../services/image_data.dart';
+
+void main() {
+  testWidgets('Headers', (WidgetTester tester) async {
+    createHttpClient = () => new http.MockClient((http.BaseRequest request) {
+          expect(request.headers, <String, String>{'flutter': 'flutter'});
+          return new Future<http.Response>.value(new http.Response.bytes(
+              kTransparentImage, 200,
+              request: request));
+        });
+    await tester.pumpWidget(new Image.network(
+      'https://www.example.com/images/frame.png',
+      headers: <String, String>{'flutter': 'flutter'},
+    ));
+  });
+}