fixes needed to get smoke tests passing

pkg/smoke/test/codegen/testing_resolver_utils.dart

Index: pkg/smoke/test/codegen/testing_resolver_utils.dart
diff --git a/pkg/smoke/test/codegen/testing_resolver_utils.dart b/pkg/smoke/test/codegen/testing_resolver_utils.dart
index 7a76614f5dc030967df81548152f76d7e5f1434f..5ae808a19eedd881d98dad6361597a469cc51a9f 100644
--- a/pkg/smoke/test/codegen/testing_resolver_utils.dart
+++ b/pkg/smoke/test/codegen/testing_resolver_utils.dart
@@ -62,11 +62,13 @@ class _SimpleUriResolver implements UriResolver {
 }
 
 class _SimpleSource extends Source {
+  final Uri uri;
   final String path;
   final String rawContents;
   final Map<String, Source> allSources;
 
-  _SimpleSource(this.path, this.rawContents, this.allSources);
+  _SimpleSource(this.path, this.rawContents, this.allSources)
+      : uri = Uri.parse('file:///path');
 
   operator ==(other) => other is _SimpleSource &&
       rawContents == other.rawContents;
@@ -86,9 +88,11 @@ class _SimpleSource extends Source {
   // Since this is just for simple tests we just restricted this mock
   // to root-relative imports. For more sophisticated stuff, you should be
   // using the test helpers in `package:code_transformers`.
-  Source resolveRelative(Uri uri) {
-    if (uri.path.startsWith('/')) return allSources['${uri.path}'];
-    throw new UnimplementedError('relative URIs not supported: $uri');
+  Uri resolveRelative(Uri uri) {
+    if (!uri.path.startsWith('/')) {
+      throw new UnimplementedError('relative URIs not supported: $uri');
+    }
+    return uri;
   }
 
   void getContentsToReceiver(Source_ContentReceiver receiver) {