chromeos: Make system tray audio item observe CrasAudioHandler directly

ash/common/system/chromeos/audio/tray_audio_unittest.cc

Index: ash/common/system/chromeos/audio/tray_audio_unittest.cc
diff --git a/ash/common/system/chromeos/audio/tray_audio_unittest.cc b/ash/common/system/chromeos/audio/tray_audio_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e0a21acf61ec74f4a258158d85581e6e7d871333
--- /dev/null
+++ b/ash/common/system/chromeos/audio/tray_audio_unittest.cc
@@ -0,0 +1,31 @@
+// 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 "ash/common/system/chromeos/audio/tray_audio.h"
+
+#include "ash/common/system/tray/system_tray.h"
+#include "ash/common/test/ash_test.h"
+
+namespace ash {
+
+using TrayAudioTest = AshTest;
+
+// Tests that the volume popup view can be explicitly shown.
+TEST_F(TrayAudioTest, ShowPopUpVolumeView) {
+  TrayAudio* tray_audio = GetPrimarySystemTray()->GetTrayAudio();
+  ASSERT_TRUE(tray_audio);
+
+  // The volume popup is not visible initially.
+  EXPECT_FALSE(tray_audio->volume_view_for_testing());
+  EXPECT_FALSE(tray_audio->pop_up_volume_view_for_testing());
+
+  // Simulate ARC asking to show the volume view.
+  TrayAudio::ShowPopUpVolumeView();
+
+  // Volume view is now visible.
+  EXPECT_TRUE(tray_audio->volume_view_for_testing());
+  EXPECT_TRUE(tray_audio->pop_up_volume_view_for_testing());
+}
+
+}  // namespace ash