Early initialize recording on the ADM from WebRtcVoiceMediaChannel.

webrtc/media/engine/webrtcvoiceengine.cc

Index: webrtc/media/engine/webrtcvoiceengine.cc
diff --git a/webrtc/media/engine/webrtcvoiceengine.cc b/webrtc/media/engine/webrtcvoiceengine.cc
index 21094fde4d45af8baed7c5228237a5caba363e04..4fcfdb8f7e6fe8ffe87a1d4318dbf91ba0ad312e 100644
--- a/webrtc/media/engine/webrtcvoiceengine.cc
+++ b/webrtc/media/engine/webrtcvoiceengine.cc
@@ -1078,6 +1078,12 @@ int WebRtcVoiceEngine::CreateVoEChannel() {
   return voe_wrapper_->base()->CreateChannel(voe_config_);
 }
 
+webrtc::AudioDeviceModule* WebRtcVoiceEngine::adm() {
+  RTC_DCHECK(worker_thread_checker_.CalledOnValidThread());
+  RTC_DCHECK(adm_);
+  return adm_;
+}
+
 class WebRtcVoiceMediaChannel::WebRtcAudioSendStream
     : public AudioSource::Sink {
  public:
@@ -1800,9 +1806,17 @@ void WebRtcVoiceMediaChannel::SetSend(bool send) {
     return;
   }
 
-  // Apply channel specific options when channel is enabled for sending.
+  // Apply channel specific options, and initialize the ADM for recording (this
+  // may take time on some platforms, e.g. Android).
   if (send) {
     engine()->ApplyOptions(options_);
+
+    // InitRecording() will return an error if the ADM is already recording.
+    if (!engine()->adm()->Recording()) {

[Taylor Brandstetter, 2016/04/01 18:41:02]

Shouldn't this call "RecordingIsInitialized"?

[the sun, 2016/04/01 21:35:40]

Actually, it looks like both must be checked. Looking at the various ADM
implementations of InitRecording(), most will return -1 if we're already
recording, but 0 if we're already initialized (see e.g.
audio_device_alsa_linux.cc, audio_device_mac.cc, audio_device_core_win.cc). But
looking closer at the Android and iOS implementations (audio_record_jni.cc,
WebRtcAudioRecord.java, audio_device_ios.mm), those will instead DCHECK that the
device is neither recording nor initialized for recording.

+      if (engine()->adm()->InitRecording() != 0) {
+        LOG(LS_WARNING) << "Failed to initialize recording";
+      }
+    }
   }
 
   // Change the settings on each send channel.