Don't switch to fake audio output until stream open fails.

media/audio/audio_manager_base.cc

 // Copyright (c) 2012 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 "media/audio/audio_manager_base.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
 #include "base/message_loop_proxy.h"
@@ skipping 86 matching lines @@
   // importantly it prevents instability on certain systems.
   // See bug: http://crbug.com/30242.
   if (num_output_streams_ >= max_num_output_streams_) {
     DLOG(ERROR) << "Number of opened output audio streams "
                 << num_output_streams_
                 << " exceed the max allowed number "
                 << max_num_output_streams_;
     return NULL;
   }
 
-  // If there are no audio output devices we should use a FakeAudioOutputStream
-  // to ensure video playback continues to work.
-  bool audio_output_disabled =
-      params.format() == AudioParameters::AUDIO_FAKE ||
-      !HasAudioOutputDevices();

[scherkus (not reviewing), 2013/02/15 18:43:37]

FYI this appeared to be the only production code use of HasAudioOutputDevices()
-- the rest were unit tests

now that we have proper fallback support, technically we could remove the check
from tests and they'd run again a fake device. not sure how useful that is
though.

[DaleCurtis, 2013/02/15 18:51:39]

Yeah, that's why I was looking at this originally. I think we can remove the
method, but we definitely can't remove HasAudioInputDevices(), so I'm wondering
if it it's best to keep both for symmetry. I believe most implementations use a
common "find devices" method and vary the input vs output parameter.

-
   AudioOutputStream* stream = NULL;
   if (virtual_audio_input_stream_) {
 #if defined(OS_IOS)
     // We do not currently support iOS. It does not link.
     NOTIMPLEMENTED();
     return NULL;
 #else
     stream = new VirtualAudioOutputStream(
         params, message_loop_, virtual_audio_input_stream_,
         base::Bind(&AudioManagerBase::ReleaseVirtualOutputStream,
                    base::Unretained(this)));
 #endif
-  } else if (audio_output_disabled) {
+  } else if (params.format() == AudioParameters::AUDIO_FAKE) {
     stream = FakeAudioOutputStream::MakeFakeStream(this, params);
   } else if (params.format() == AudioParameters::AUDIO_PCM_LINEAR) {
     stream = MakeLinearOutputStream(params);
   } else if (params.format() == AudioParameters::AUDIO_PCM_LOW_LATENCY) {
     stream = MakeLowLatencyOutputStream(params);
   }
 
   if (stream)
     ++num_output_streams_;
 
@@ skipping 278 matching lines @@
   output_listeners_.RemoveObserver(listener);
 }
 
 void AudioManagerBase::NotifyAllOutputDeviceChangeListeners() {
   DCHECK(message_loop_->BelongsToCurrentThread());
   DVLOG(1) << "Firing OnDeviceChange() notifications.";
   FOR_EACH_OBSERVER(AudioDeviceListener, output_listeners_, OnDeviceChange());
 }
 
 }  // namespace media