Allow transformers to exclude and include assets.

sdk/lib/_internal/pub/test/transformer/exclusion/works_on_dart2js_test.dart

Index: sdk/lib/_internal/pub/test/transformer/exclusion/works_on_dart2js_test.dart
diff --git a/sdk/lib/_internal/pub/test/transformer/dart2js/does_not_compile_until_its_output_is_requested_test.dart b/sdk/lib/_internal/pub/test/transformer/exclusion/works_on_dart2js_test.dart
similarity index 51%
copy from sdk/lib/_internal/pub/test/transformer/dart2js/does_not_compile_until_its_output_is_requested_test.dart
copy to sdk/lib/_internal/pub/test/transformer/exclusion/works_on_dart2js_test.dart
index e25a36852896dee7c333ce9580343fb145c0d0f7..aedfbf9785baaaf75d36c123819080ab5681c680 100644
--- a/sdk/lib/_internal/pub/test/transformer/dart2js/does_not_compile_until_its_output_is_requested_test.dart
+++ b/sdk/lib/_internal/pub/test/transformer/exclusion/works_on_dart2js_test.dart
@@ -12,28 +12,32 @@ import '../../serve/utils.dart';
 
 main() {
   initConfig();
-  integration("does not compile until its output is requested", () {
+  integration("works on the dart2js transformer", () {
     d.dir(appPath, [
       d.pubspec({
         "name": "myapp",
-        "version": "0.0.1",
+        "transformers": [
+          {
+            "\$dart2js": {
+              "\$include": ["web/a.dart", "web/b.dart"],
+              "\$exclude": "web/a.dart"
+            }
+          }
+        ]
       }),
       d.dir("web", [
-        d.file("syntax-error.dart", "syntax error")
+        d.file("a.dart", "void main() => print('hello');"),
+        d.file("b.dart", "void main() => print('hello');"),
+        d.file("c.dart", "void main() => print('hello');")
       ])
     ]).create();
 
     createLockFile('myapp', pkg: ['barback']);
 
-    var server = pubServe();
-    server.stdout.expect("Build completed successfully");
-
-    // Once we request the output, it should start compiling and fail.
-    requestShould404("syntax-error.dart.js");
-    server.stdout.expect(emitsLines(
-        "[Info from Dart2JS]:\n"
-        "Compiling myapp|web/syntax-error.dart...\n"
-        "Build completed with 1 errors."));
+    pubServe();
+    requestShould404("a.dart.js");
+    requestShouldSucceed("b.dart.js", isNot(isEmpty));
+    requestShould404("c.dart.js");
     endPubServe();
   });
 }