Translate package URIs to resource URIs for diagnostics.

tests/compiler/dart2js/show_package_warnings_test.dart

Index: tests/compiler/dart2js/show_package_warnings_test.dart
diff --git a/tests/compiler/dart2js/show_package_warnings_test.dart b/tests/compiler/dart2js/show_package_warnings_test.dart
index eb9a441fc9b202206103fbee5e8552b08e9acf81..de518f9ccc1360e28e488810af9056a90c070ffc 100644
--- a/tests/compiler/dart2js/show_package_warnings_test.dart
+++ b/tests/compiler/dart2js/show_package_warnings_test.dart
@@ -69,14 +69,26 @@ void test(List<Uri> entryPoints,
                   'Unexpected errors: ${collector.errors}');
     Expect.equals(warnings, collector.warnings.length,
                   'Unexpected warnings: ${collector.warnings}');
+    checkUriSchemes(collector.warnings);
     Expect.equals(hints, collector.hints.length,
                   'Unexpected hints: ${collector.hints}');
+    checkUriSchemes(collector.hints);
     Expect.equals(infos, collector.infos.length,
                   'Unexpected infos: ${collector.infos}');
+    checkUriSchemes(collector.infos);
     print('==================================================================');
   }));
 }
 
+void checkUriSchemes(Iterable<DiagnosticMessage> messages) {
+  for (DiagnosticMessage message in messages) {
+    if (message.uri != null) {
+      Expect.notEquals('package', message.uri.scheme,
+          "Unexpected package uri `${message.uri}` in message: $message");
+    }
+  }
+}
+
 void main() {
   test([Uri.parse('memory:main.dart')],
        showPackageWarnings: true,