Re-enables three WebRTC unit tests in content

content/renderer/media/webrtc_audio_device_impl.cc

 // Copyright 2013 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/media/webrtc_audio_device_impl.h"
 
 #include "base/bind.h"
 #include "base/metrics/histogram.h"
 #include "base/strings/string_util.h"
 #include "base/win/windows_version.h"
@@ skipping 102 matching lines @@
   DCHECK(thread_checker_.CalledOnValidThread());
 }
 
 void WebRtcAudioDeviceImpl::RenderData(uint8* audio_data,
                                        int number_of_channels,
                                        int number_of_frames,
                                        int audio_delay_milliseconds) {
   DCHECK_LE(number_of_frames, output_buffer_size());
   {
     base::AutoLock auto_lock(lock_);
+    DCHECK(audio_transport_callback_);
     // Store the reported audio delay locally.
     output_delay_ms_ = audio_delay_milliseconds;
   }
 
   const int channels = number_of_channels;
   DCHECK_LE(channels, output_channels());
 
   int samples_per_sec = output_sample_rate();
   int samples_per_10_msec = (samples_per_sec / 100);
   int bytes_per_sample = output_audio_parameters_.bits_per_sample() / 8;
@@ skipping 348 matching lines @@
   for (CapturerList::const_iterator iter = capturers_.begin();
        iter != capturers_.end(); ++iter) {
     if (!(*iter)->device_id().empty())
       return *iter;
   }
 
   return NULL;
 }
 
 }  // namespace content