Inline the single test asset. (#2681)

diff --git a/test/asset/out-of-date.snapshot.dart2 b/test/asset/out-of-date.snapshot.dart2
deleted file mode 100644
index 595efe3..0000000
--- a/test/asset/out-of-date.snapshot.dart2
+++ /dev/null
Binary files differ
diff --git a/test/descriptor.dart b/test/descriptor.dart
index 73518ee..8f5c25a 100644
--- a/test/descriptor.dart
+++ b/test/descriptor.dart
@@ -3,8 +3,9 @@
 // BSD-style license that can be found in the LICENSE file.
 
 /// Pub-specific test descriptors.
+import 'dart:convert';
+
 import 'package:oauth2/oauth2.dart' as oauth2;
-import 'package:pub/src/io.dart';
 import 'package:pub/src/package_config.dart';
 import 'package:test_descriptor/test_descriptor.dart';
 import 'package:meta/meta.dart';
@@ -41,8 +42,21 @@
 /// Returns a descriptor of a snapshot that can't be run by the current VM.
 ///
 /// This snapshot was generated using version 2.0.0-dev.58.0 of the VM.
-FileDescriptor outOfDateSnapshot(String name) =>
-    file(name, readBinaryFile(testAssetPath('out-of-date.snapshot.dart2')));
+FileDescriptor outOfDateSnapshot(String name) => file(
+      name,
+      base64.decode(
+        'kKvN7wAAAAYBAAEAAQAAAAAAAAABBgMBBh8AAQEAAAABA'
+        'wofAAAAAAAAAFwBShABHhAGAQABJwIAAAAAEwAAAAAAAA'
+        'AVAAAAOQAAAAEAAAACAAAAJWZpbGU6Ly8vVXNlcnMvcm5'
+        '5c3Ryb20vdGVtcC90ZW1wLmRhcnQgdm9pZCBtYWluKCkg'
+        'PT4gcHJpbnQoJ2hlbGxvIScpOwoDACABAAAAUQAAAFQGA'
+        'AMBBAIBAAUEBAUGAAAAAAcABAovN0BFbWFpbmhlbGxvIW'
+        'ZpbGU6Ly8vVXNlcnMvcm55c3Ryb20vdGVtcC90ZW1wLmR'
+        'hcnRAbWV0aG9kc2RhcnQ6Y29yZXByaW50AAAAAE0AAACn'
+        'AAAAtAAAALQAAAC4AAABBQAAAAMAAAAJAAAATQAAAAEAA'
+        'AEy',
+      ),
+    );
 
 /// Describes a file named `pubspec.yaml` with the given YAML-serialized
 /// [contents], which should be a serializable object.
diff --git a/test/test_pub.dart b/test/test_pub.dart
index f1d1010..5c71a82 100644
--- a/test/test_pub.dart
+++ b/test/test_pub.dart
@@ -670,9 +670,6 @@
   return package;
 }
 
-/// Resolves [target] relative to the path to pub's `test/asset` directory.
-String testAssetPath(String target) => p.join(pubRoot, 'test', 'asset', target);
-
 /// Returns a Map in the format used by the pub.dartlang.org API to represent a
 /// package version.
 ///