Add a "pub global run" command.

sdk/lib/_internal/pub/test/global/run/runs_transformer_test.dart

Index: sdk/lib/_internal/pub/test/global/run/runs_transformer_test.dart
diff --git a/sdk/lib/_internal/pub/test/run/runs_a_generated_script_test.dart b/sdk/lib/_internal/pub/test/global/run/runs_transformer_test.dart
similarity index 64%
copy from sdk/lib/_internal/pub/test/run/runs_a_generated_script_test.dart
copy to sdk/lib/_internal/pub/test/global/run/runs_transformer_test.dart
index daedf2567873e462f16c90f5f8020a0ae9cb2585..79a181c67500e7c666bd6cc0c3b4134edf14b524 100644
--- a/sdk/lib/_internal/pub/test/run/runs_a_generated_script_test.dart
+++ b/sdk/lib/_internal/pub/test/global/run/runs_transformer_test.dart
@@ -2,9 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import '../descriptor.dart' as d;
-import '../test_pub.dart';
-import 'utils.dart';
+import '../../descriptor.dart' as d;
+import '../../test_pub.dart';
 
 const TRANSFORMER = """
 import 'dart:async';
@@ -18,7 +17,7 @@ class DartTransformer extends Transformer {
 
   void apply(Transform transform) {
     transform.addOutput(new Asset.fromString(
-        new AssetId("myapp", "bin/script.dart"),
+        new AssetId("foo", "bin/script.dart"),
         "void main() => print('generated');"));
   }
 }
@@ -27,22 +26,20 @@ class DartTransformer extends Transformer {
 main() {
   initConfig();
   withBarbackVersions("any", () {
-    integration('runs a script generated from scratch by a transformer', () {
-      d.dir(appPath, [
+    integration('runs a global script generated by a transformer', () {
+      makeGlobalPackage("foo", "1.0.0", [
         d.pubspec({
-          "name": "myapp",
-          "transformers": ["myapp/src/transformer"]
+          "name": "foo",
+          "version": "1.0.0",
+          "transformers": ["foo/src/transformer"]
         }),
         d.dir("lib", [d.dir("src", [
           d.file("transformer.dart", TRANSFORMER),
           d.file("primary.in", "")
         ])])
-      ]).create();
+      ], pkg: ['barback']);
 
-      createLockFile('myapp', pkg: ['barback']);
-
-      var pub = pubRun(args: ["script"],
-          transformers: ["myapp/src/transformer"]);
+      var pub = pubRun(global: true, args: ["foo", "script"]);
 
       pub.stdout.expect("generated");
       pub.shouldExit();