Change "typedef" to "class" in core library and related tests.

sdk/lib/_internal/compiler/implementation/tree/unparser.dart

Index: sdk/lib/_internal/compiler/implementation/tree/unparser.dart
diff --git a/sdk/lib/_internal/compiler/implementation/tree/unparser.dart b/sdk/lib/_internal/compiler/implementation/tree/unparser.dart
index 259d4d010b8408e489c2214b07a9a7e73cc3ebb0..0ca2f98566536b13b4baa647c665e43f1c8e1bf2 100644
--- a/sdk/lib/_internal/compiler/implementation/tree/unparser.dart
+++ b/sdk/lib/_internal/compiler/implementation/tree/unparser.dart
@@ -84,16 +84,16 @@ class Unparser implements Visitor {
   }
 
   visitNamedMixinApplication(NamedMixinApplication node) {
-    sb.write('typedef ');
+    if (!node.modifiers.nodes.isEmpty) {
+      visit(node.modifiers);
+      sb.write(' ');
+    }
+    sb.write('class ');
     visit(node.name);
     if (node.typeParameters != null) {
       visit(node.typeParameters);
     }
     sb.write(' = ');
-    if (!node.modifiers.nodes.isEmpty) {
-      visit(node.modifiers);
-      sb.write(' ');
-    }
     visit(node.mixinApplication);
     if (node.interfaces != null) {
       sb.write(' implements ');