Remove remaining calls to deprecated MessageLoop methods.

content/renderer/media/media_stream_audio_processor.cc

Index: content/renderer/media/media_stream_audio_processor.cc
diff --git a/content/renderer/media/media_stream_audio_processor.cc b/content/renderer/media/media_stream_audio_processor.cc
index c02696e068432520252b7d2d6d31ef0a2694735c..9b8eaf35ffc0b438b550a88999166fd3653e47ea 100644
--- a/content/renderer/media/media_stream_audio_processor.cc
+++ b/content/renderer/media/media_stream_audio_processor.cc
@@ -11,6 +11,7 @@
 #include "base/command_line.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
+#include "base/single_thread_task_runner.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/trace_event/trace_event.h"
 #include "build/build_config.h"
@@ -761,7 +762,7 @@ int MediaStreamAudioProcessor::ProcessData(const float* const* process_ptrs,
     base::subtle::Release_Store(&typing_detected_, detected);
   }
 
-  main_thread_message_loop_->PostTask(
+  main_thread_message_loop_->task_runner()->PostTask(
       FROM_HERE, base::Bind(&MediaStreamAudioProcessor::UpdateAecStats, this));
 
   // Return 0 if the volume hasn't been changed, and otherwise the new volume.