Support audio output device enumeration and selection in PPAPI

content/renderer/pepper/pepper_audio_controller.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 "content/renderer/pepper/pepper_audio_controller.h"
 
+#include "content/renderer/pepper/pepper_audio_output_host.h"
 #include "content/renderer/pepper/pepper_plugin_instance_impl.h"
 #include "content/renderer/pepper/ppb_audio_impl.h"
 #include "content/renderer/render_frame_impl.h"
 
 namespace content {
 
 PepperAudioController::PepperAudioController(
     PepperPluginInstanceImpl* instance)
     : instance_(instance) {
   DCHECK(instance_);
 }
 
 PepperAudioController::~PepperAudioController() {
   if (instance_)
     OnPepperInstanceDeleted();
 }
 
 void PepperAudioController::AddInstance(PPB_Audio_Impl* audio) {
   if (!instance_)
     return;
   if (ppb_audios_.count(audio))
     return;
 
-  if (ppb_audios_.empty()) {
-    RenderFrameImpl* render_frame = instance_->render_frame();
-    if (render_frame)
-      render_frame->PepperStartsPlayback(instance_);
-  }
+  StartPlaybackIfFirstInstance();
 
   ppb_audios_.insert(audio);
 }
 
+void PepperAudioController::AddInstance(PepperAudioOutputHost* audio_output) {
+  if (!instance_)
+    return;
+  if (audio_output_hosts_.count(audio_output))
+    return;
+
+  StartPlaybackIfFirstInstance();
+
+  audio_output_hosts_.insert(audio_output);
+}
+
 void PepperAudioController::RemoveInstance(PPB_Audio_Impl* audio) {
   if (!instance_)
     return;
   if (!ppb_audios_.count(audio))
     return;
 
   ppb_audios_.erase(audio);
 
-  if (ppb_audios_.empty())
-    NotifyPlaybackStopsOnEmpty();
+  StopPlaybackIfLastInstance();
+}
+
+void PepperAudioController::RemoveInstance(
+    PepperAudioOutputHost* audio_output) {
+  if (!instance_)
+    return;
+  if (!audio_output_hosts_.count(audio_output))
+    return;
+
+  audio_output_hosts_.erase(audio_output);
+
+  StopPlaybackIfLastInstance();
 }
 
 void PepperAudioController::SetVolume(double volume) {
   if (!instance_)
     return;
 
   for (auto* ppb_audio : ppb_audios_)
     ppb_audio->SetVolume(volume);
+
+  for (auto* audio_output_host : audio_output_hosts_)
+    audio_output_host->SetVolume(volume);
 }
 
 void PepperAudioController::OnPepperInstanceDeleted() {
   DCHECK(instance_);
 
-  if (!ppb_audios_.empty())
-    NotifyPlaybackStopsOnEmpty();
+  StopPlaybackIfLastInstance();

[bbudge, 2017/03/31 00:24:59]

I'm sorry if I led you astray here, the original test is !ppb_audios_.empty()
while StopPlayback tests the reverse condition. So you should call
NotifyPlaybackStopsOnEmpty if either array is non-empty.

[Xing, 2017/03/31 18:23:29]

It's totally my mistake, sorry about my careless copy/paste.

Fixed.

 
   ppb_audios_.clear();
+  audio_output_hosts_.clear();
   instance_ = nullptr;
 }
 
 void PepperAudioController::NotifyPlaybackStopsOnEmpty() {
   DCHECK(instance_);
 
   RenderFrameImpl* render_frame = instance_->render_frame();
   if (render_frame)
     render_frame->PepperStopsPlayback(instance_);
 }
 
+void PepperAudioController::StartPlaybackIfFirstInstance() {
+  if (instance_)
+    return;

[bbudge, 2017/03/31 00:24:59]

DCHECK(instance_);

Rather than if - statement, because of the tests in calling code, it's a
programming error if this is null here.

[Xing, 2017/03/31 18:23:29]

Done.

+
+  if (audio_output_hosts_.empty() && ppb_audios_.empty()) {
+    RenderFrameImpl* render_frame = instance_->render_frame();
+    if (render_frame)
+      render_frame->PepperStartsPlayback(instance_);
+  }
+}
+
+void PepperAudioController::StopPlaybackIfLastInstance() {
+  if (instance_)
+    return;

[bbudge, 2017/03/31 00:24:59]

DCHECK(instance_)

[Xing, 2017/03/31 18:23:29]

Done.

+
+  if (audio_output_hosts_.empty() && ppb_audios_.empty())
+    NotifyPlaybackStopsOnEmpty();
+}
+
 }  // namespace content