Support transformers that depend on other transformers.

sdk/lib/_internal/pub/test/test_pub.dart

Index: sdk/lib/_internal/pub/test/test_pub.dart
diff --git a/sdk/lib/_internal/pub/test/test_pub.dart b/sdk/lib/_internal/pub/test/test_pub.dart
index 64c1682e1a1128940652aa8c4fe7a307f0adfd57..897b69e92fce68bd28ef63ce42685b7d1dc8e0a1 100644
--- a/sdk/lib/_internal/pub/test/test_pub.dart
+++ b/sdk/lib/_internal/pub/test/test_pub.dart
@@ -607,12 +607,20 @@ void ensureGit() {
 
 /// Create a lock file for [package] without running `pub install`.
 ///
-/// This creates a lock file with only path dependencies. [dependencies] is a
-/// map of dependency names to paths. [pkg] is a list of packages in the Dart
-/// repo's "pkg" directory; each package listed here and all its dependencies
-/// will be linked to the version in the Dart repo.
-void createLockFile(String package, Map<String, String> dependencies,
-    {Iterable<String> pkg}) {
+/// This creates a lock file with only path dependencies. [sandbox] is a list of
+/// dependencies to be found in the sandbox directory. [pkg] is a list of
+/// packages in the Dart repo's "pkg" directory; each package listed here and
+/// all its dependencies will be linked to the version in the Dart repo.
+void createLockFile(String package, {Iterable<String> sandbox,
+    Iterable<String> pkg}) {
+  var dependencies = {};
+
+  if (sandbox != null) {
+    for (var package in sandbox) {
+      dependencies[package] = '../$package';
+    }
+  }
+
   if (pkg != null) {
     var pkgDir = path.absolute(path.join(
         path.dirname(Platform.executable),