Add support for building on Fuchsia (#6415)

This patch makes it possible to build Flutter apps that use the framework on
Fuchsia.

packages/flutter/BUILD.gn

@@ -0,0 +1,20 @@
+# Copyright 2016 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("//build/dart/dart_package.gni")
+
+dart_package("flutter") {
+  package_name = "flutter"
+
+  source_dir = "lib"
+
+  deps = [
+    "//third_party/dart-pkg/pub/async",
+    "//third_party/dart-pkg/pub/collection",
+    "//third_party/dart-pkg/pub/http_parser",
+    "//third_party/dart-pkg/pub/intl",
+    "//third_party/dart-pkg/pub/meta",
+    "//third_party/dart-pkg/pub/vector_math",
+  ]
+}

packages/flutter_tools/bin/fuchsia_builder.dart

@@ -9,6 +9,7 @@ import 'package:args/args.dart';
 
 import '../lib/src/base/context.dart';
 import '../lib/src/base/logger.dart';
+import '../lib/src/cache.dart';
 import '../lib/src/flx.dart';
 import '../lib/src/globals.dart';
 
@@ -48,6 +49,7 @@ Future<Null> main(List<String> args) async {
     printError('Missing option! All options must be specified.');
     exit(1);
   }
+  Cache.flutterRoot = Platform.environment['FLUTTER_ROOT'];
   String outputPath = argResults[_kOptionOutput];
   final int buildResult = await build(
     snapshotterPath: argResults[_kOptionSnapshotter],

packages/flutter_tools/lib/src/asset.dart

@@ -68,10 +68,12 @@ class AssetBundle {
   Future<int> build({
     String manifestPath: defaultManifestPath,
     String workingDirPath,
+    String packagesPath,
     bool includeRobotoFonts: true,
     bool reportLicensedPackages: false
   }) async {
     workingDirPath ??= getAssetBuildDirectory();
+    packagesPath ??= path.absolute(PackageMap.globalPackagesPath);
     Object manifest = _loadFlutterYamlManifest(manifestPath);
     if (manifest == null) {
       // No manifest file found for this application.
@@ -88,8 +90,7 @@ class AssetBundle {
 
     _lastBuildTimestamp = new DateTime.now();
 
-    final PackageMap packageMap =
-        new PackageMap(path.join(assetBasePath, '.packages'));
+    final PackageMap packageMap = new PackageMap(packagesPath);
 
     Map<_Asset, List<_Asset>> assetVariants = _parseAssets(
       packageMap,

packages/flutter_tools/lib/src/flx.dart

@@ -118,6 +118,7 @@ Future<int> build({
     outputPath: outputPath,
     privateKeyPath: privateKeyPath,
     workingDirPath: workingDirPath,
+    packagesPath: packagesPath,
     includeRobotoFonts: includeRobotoFonts,
     reportLicensedPackages: reportLicensedPackages
   );
@@ -129,11 +130,13 @@ Future<int> assemble({
   String outputPath,
   String privateKeyPath: defaultPrivateKeyPath,
   String workingDirPath,
+  String packagesPath,
   bool includeRobotoFonts: true,
   bool reportLicensedPackages: false
 }) async {
   outputPath ??= defaultFlxOutputPath;
   workingDirPath ??= getAssetBuildDirectory();
+  packagesPath ??= path.absolute(PackageMap.globalPackagesPath);
   printTrace('Building $outputPath');
 
   // Build the asset bundle.
@@ -141,6 +144,7 @@ Future<int> assemble({
   int result = await assetBundle.build(
     manifestPath: manifestPath,
     workingDirPath: workingDirPath,
+    packagesPath: packagesPath,
     includeRobotoFonts: includeRobotoFonts,
     reportLicensedPackages: reportLicensedPackages
   );