[Chromoting] GetHostAttributes with tests

remoting/host/host_traits_unittest.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "remoting/host/host_traits.h"
+
+#include <string>
+
+#include "base/bind.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace remoting {
+
+// Ensures there is no DCHECK failure or crash in Register() and Callbacks.
+TEST(HostTraitsTest, Sanity) {
+  host_traits().ToString();
+}
+
+TEST(HostTraitsTest, DynamicValuesShouldBeEvaluated) {
+  const char trait_key[] = "A-Fake-Trait-Key-In-Host-Traits-Unit-Test";
+  bool value = false;
+  int evaluated_times = 0;
+
+  host_traits().Register(trait_key,
+                         base::Bind([](int* evaluated_times, bool* value) {
+                                        (*evaluated_times)++;
+                                        return *value;
+                                    }, &evaluated_times, &value));
+
+  std::string result = host_traits().ToString();
+  ASSERT_FALSE(HostTraits::ContainsTrait(result, trait_key));
+  ASSERT_EQ(evaluated_times, 1);
+
+  value = true;
+  result = host_traits().ToString();
+  ASSERT_TRUE(HostTraits::ContainsTrait(result, trait_key));
+  ASSERT_EQ(evaluated_times, 2);
+
+  host_traits().Erase(trait_key);
+}
+
+}  // namespace remoting