Place flutter_gpu in the package cache. (#149299)

Resolves flutter/flutter#131711.

Fetch https://storage.googleapis.com/flutter_infra_release/flutter/${engine_version}/flutter_gpu.zip and extract it into the package cache.

Cannot function until flutter/engine#53107 has been merged/rolled into the framework.

Author: bdero

packages/flutter_tools/lib/src/flutter_cache.dart

@@ -231,7 +231,7 @@ class FlutterSdk extends EngineCachedArtifact {
   final Platform _platform;
 
   @override
-  List<String> getPackageDirs() => const <String>['sky_engine'];
+  List<String> getPackageDirs() => const <String>['sky_engine', 'flutter_gpu'];
 
   @override
   List<List<String>> getBinaryDirs() {

packages/flutter_tools/test/general.shard/cache_test.dart

@@ -393,6 +393,44 @@ void main() {
     expect(operatingSystemUtils.chmods, <List<String>>[<String>['/.tmp_rand0/flutter_cache_test_artifact.rand0/bin_dir', 'a+r,a+x']]);
   });
 
+  testWithoutContext('EngineCachedArtifact downloads package zip from expected URL', () async {
+    final FakeOperatingSystemUtils operatingSystemUtils = FakeOperatingSystemUtils();
+    final FileSystem fileSystem = MemoryFileSystem.test();
+    final Directory artifactDir = fileSystem.systemTempDirectory.createTempSync('flutter_cache_test_artifact.');
+    final Directory downloadDir = fileSystem.systemTempDirectory.createTempSync('flutter_cache_test_download.');
+    final FakeSecondaryCache cache = FakeSecondaryCache()
+      ..artifactDirectory = artifactDir
+      ..downloadDir = downloadDir;
+    artifactDir.childDirectory('pkg').createSync();
+
+    final FakeCachedArtifact artifact = FakeCachedArtifact(
+      cache: cache,
+      binaryDirs: <List<String>>[],
+      packageDirs: <String>[
+        'package_dir',
+      ],
+      requiredArtifacts: DevelopmentArtifact.universal,
+    );
+
+    Uri? packageUrl;
+    final ArtifactUpdater artifactUpdater = FakeArtifactUpdater()
+      ..onDownloadZipArchive = (String message, Uri url, Directory location) {
+        location.childDirectory('package_dir').createSync();
+        packageUrl = url;
+      };
+
+    await artifact.updateInner(artifactUpdater, fileSystem, operatingSystemUtils);
+    expect(packageUrl, isNotNull);
+    expect(packageUrl.toString(), 'https://storage.googleapis.com/flutter_infra_release/flutter/null/package_dir.zip');
+
+    final Directory dir = fileSystem.systemTempDirectory
+        .listSync(recursive: true)
+        .whereType<Directory>()
+        .singleWhereOrNull((Directory directory) => directory.basename == 'pkg')!;
+    expect(dir.path, artifactDir.childDirectory('pkg').path);
+    expect(dir.childDirectory('package_dir').existsSync(), isTrue);
+  });
+
   testWithoutContext('Try to remove without a parent', () async {
     final FileSystem fileSystem = MemoryFileSystem.test();
     final Directory parent = fileSystem.directory('dir');