patch from issue 428303004

pkg/code_transformers/lib/src/dart_sdk.dart

Index: pkg/code_transformers/lib/src/dart_sdk.dart
diff --git a/pkg/code_transformers/lib/src/dart_sdk.dart b/pkg/code_transformers/lib/src/dart_sdk.dart
index 3438218d514ec87f7fc3656f941ace7b4899b71d..bdef955c70777e0a83a6f091e8fcd2ade95add17 100644
--- a/pkg/code_transformers/lib/src/dart_sdk.dart
+++ b/pkg/code_transformers/lib/src/dart_sdk.dart
@@ -108,11 +108,7 @@ class DartSourceProxy implements UriAnnotatedSource {
     return new DartSourceProxy(source, uri);
   }
 
-  Source resolveRelative(Uri relativeUri) {
-    // Assume that the type can be accessed via this URI, since these
-    // should only be parts for dart core files.
-    return wrap(_proxy.resolveRelative(relativeUri), uri);
-  }
+  Uri resolveRelative(Uri relativeUri) => _proxy.resolveRelative(relativeUri);
 
   bool exists() => _proxy.exists();
 
@@ -181,6 +177,11 @@ class MockDartSdk implements DartSdk {
     }
     return src;
   }
+
+  @override
+  Source fromFileUri(Uri uri) {
+    throw new UnsupportedError('MockDartSdk.fromFileUri');
+  }
 }
 
 class _MockSdkSource implements UriAnnotatedSource {
@@ -209,6 +210,6 @@ class _MockSdkSource implements UriAnnotatedSource {
 
   bool get isInSystemLibrary => true;
 
-  Source resolveRelative(Uri relativeUri) =>
+  Uri resolveRelative(Uri relativeUri) =>
       throw new UnsupportedError('not expecting relative urls in dart: mocks');
 }