Move some generic functions to AudioManagerBase to be inherited by platform-specific AudioManager***

media/audio/audio_input_volume_unittest.cc

Index: media/audio/audio_input_volume_unittest.cc
diff --git a/media/audio/audio_input_volume_unittest.cc b/media/audio/audio_input_volume_unittest.cc
index 15cb7fbc72218a9fa1b61854818071ea75a485e1..febdb78b709e14d453ee9ada4c05291e672cd8b6 100644
--- a/media/audio/audio_input_volume_unittest.cc
+++ b/media/audio/audio_input_volume_unittest.cc
@@ -97,7 +97,10 @@ TEST_F(AudioInputVolumeTest, InputVolumeTest) {
   // Retrieve a list of all available input devices.
   AudioDeviceNames device_names;
   audio_manager_->GetAudioInputDeviceNames(&device_names);
-  DCHECK(!device_names.empty());
+  if (device_names.empty()) {
+    LOG(WARNING) << "Could not find any available input device";
+    return;
+  }
 
   // Scan all available input devices and repeat the same test for all of them.
   for (AudioDeviceNames::const_iterator it = device_names.begin();