Use static dispatch for dynamic on Object methods

Fixes #510

R=jmesserly@google.com

Review URL: https://codereview.chromium.org/1919173004 .

pkg/dev_compiler/lib/src/compiler/code_generator.dart

@@ -3139,6 +3139,7 @@ class CodeGenerator extends GeneralizingAstVisitor
     // If the target may be an extension type, we also use static dispatch
     // as we don't symbolize object properties like hashCode.
     return isNullable(target) ||
+        type.isDynamic ||
         (_extensionTypes.contains(type.element) && target is! SuperExpression);
   }
 

pkg/dev_compiler/test/codegen/expect/language-all.js

@@ -67577,6 +67577,24 @@ dart_library.library('hash_map_null_key_foreach_test', null, /* Imports */[
   // Exports:
   exports.hash_map_null_key_foreach_test = hash_map_null_key_foreach_test;
 });
+dart_library.library('hashcode_dynamic_test', null, /* Imports */[
+  'dart_sdk',
+  'expect'
+], function(exports, dart_sdk, expect) {
+  'use strict';
+  const core = dart_sdk.core;
+  const dart = dart_sdk.dart;
+  const dartx = dart_sdk.dartx;
+  const expect$ = expect.expect;
+  const hashcode_dynamic_test = Object.create(null);
+  hashcode_dynamic_test.main = function() {
+    let x = 3;
+    expect$.Expect.equals(3, dart.hashCode(x));
+  };
+  dart.fn(hashcode_dynamic_test.main, dart.void, []);
+  // Exports:
+  exports.hashcode_dynamic_test = hashcode_dynamic_test;
+});
 dart_library.library('hello_dart_test', null, /* Imports */[
   'dart_sdk'
 ], function(exports, dart_sdk) {

pkg/dev_compiler/test/codegen/language/hashcode_dynamic_test.dart

@@ -0,0 +1,10 @@
+// Copyright (c) 2016, 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";
+
+void main() {
+  dynamic x = 3;
+  Expect.equals(3, x.hashCode);
+}