Handle fields/getter of mixed-in classes.

tests/compiler/dart2js/cpa_inference_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import "package:expect/expect.dart";
 import '../../../sdk/lib/_internal/compiler/implementation/scanner/scannerlib.dart';
 import '../../../sdk/lib/_internal/compiler/implementation/source_file.dart';
 import '../../../sdk/lib/_internal/compiler/implementation/types/types.dart';
 
 import "parser_helper.dart";
@@ skipping 1317 matching lines @@
   Expect.equals(
       inferredType(new TypedSelector.subclass(
           xy.rawType, foo)).simplify(result.compiler),
       new TypeMask.nonNullSubclass(bc.rawType));
 
   Selector bar = new Selector.call(buildSourceString("bar"), null, 0);
 
   Expect.isNull(inferredType(bar));
 }
 
+testMixins() {
+  final String source = r"""
+      class A {
+        foo() => "abc";
+        get x => 42;
+      }
+      class B extends Object with A {
+        bar() => foo();
+        baz() => x;
+      }
+      main() {
+        var b = new B();
+        var x = b.foo();
+        var y = b.bar();
+        var z = b.x;
+        var w = b.baz();
+        x; y; z; w;
+      }
+      """;
+  AnalysisResult result = analyze(source);
+  result.checkNodeHasType('x', [result.string]);
+  result.checkNodeHasType('y', [result.string]);
+  result.checkNodeHasType('z', [result.int]);
+  result.checkNodeHasType('w', [result.int]);
+}
+
 void main() {
   testDynamicBackDoor();
   testVariableDeclaration();
   testLiterals();
   testRedefinition();
   testIfThenElse();
   testTernaryIf();
   testWhile();
   testFor1();
   testFor2();
@@ skipping 31 matching lines @@
   testDynamicIsAbsorbing();
   testLists();
   testListWithCapacity();
   testEmptyList();
   testJsCall();
   testIsCheck();
   testSeenClasses();
   testIntDoubleNum();
   testConcreteTypeToTypeMask();
   testSelectors();
+  testMixins();
 }