Store the async-await compiled pub code directly in the repo.

sdk/lib/_internal/pub_generated/test/serve/web_socket/path_to_urls_errors_test.dart

+library pub_tests;
+import 'package:json_rpc_2/error_code.dart' as rpc_error_code;
+import 'package:path/path.dart' as p;
+import '../../descriptor.dart' as d;
+import '../../test_pub.dart';
+import '../utils.dart';
+main() {
+  initConfig();
+  integration("pathToUrls errors on bad inputs", () {
+    d.dir(
+        "foo",
+        [
+            d.libPubspec("foo", "1.0.0"),
+            d.dir("web", [d.file("foo.txt", "foo")])]).create();
+    d.dir(appPath, [d.appPubspec({
+        "foo": {
+          "path": "../foo"
+        }
+      }),
+          d.file("top-level.txt", "top-level"),
+          d.dir("bin", [d.file("foo.txt", "foo")]),
+          d.dir("lib", [d.file("myapp.dart", "myapp")])]).create();
+    pubServe(shouldGetFirst: true);
+    expectWebSocketError("pathToUrls", {
+      "path": 123
+    },
+        rpc_error_code.INVALID_PARAMS,
+        'Parameter "path" for method "pathToUrls" must be a string, but was ' '123.');
+    expectWebSocketError("pathToUrls", {
+      "path": "main.dart",
+      "line": 12.34
+    },
+        rpc_error_code.INVALID_PARAMS,
+        'Parameter "line" for method "pathToUrls" must be an integer, but was '
+            '12.34.');
+    expectNotServed(p.join('bin', 'foo.txt'));
+    expectNotServed(p.join('nope', 'foo.txt'));
+    expectNotServed(p.join("..", "bar", "lib", "bar.txt"));
+    expectNotServed(p.join("..", "foo", "web", "foo.txt"));
+    endPubServe();
+  });
+}
+void expectNotServed(String path) {
+  expectWebSocketError("pathToUrls", {
+    "path": path
+  }, NOT_SERVED, 'Asset path "$path" is not currently being served.');
+}