Fix error message for library name mismatch.

sdk/lib/_internal/compiler/implementation/elements/modelx.dart

Index: sdk/lib/_internal/compiler/implementation/elements/modelx.dart
diff --git a/sdk/lib/_internal/compiler/implementation/elements/modelx.dart b/sdk/lib/_internal/compiler/implementation/elements/modelx.dart
index 19759c97244ffc2cd4ed2c6bc2c35b9eda7f1be9..2d1bf8f456e5b5a4fb8af4d763d9bc502c060a7b 100644
--- a/sdk/lib/_internal/compiler/implementation/elements/modelx.dart
+++ b/sdk/lib/_internal/compiler/implementation/elements/modelx.dart
@@ -507,8 +507,8 @@ class CompilationUnitElementX extends ElementX
     partTag = tag;
     LibraryName libraryTag = getLibrary().libraryTag;
     if (libraryTag != null) {
-      String expectedName = tag.name.toString();
-      String actualName = libraryTag.name.toString();
+      String actualName = tag.name.toString();
+      String expectedName = libraryTag.name.toString();
       if (expectedName != actualName) {
         listener.reportMessage(
             listener.spanFromSpannable(tag.name),