Preparational work for an upcoming addition of a threadchecking scheme for APM

webrtc/modules/audio_processing/echo_cancellation_impl.h

Index: webrtc/modules/audio_processing/echo_cancellation_impl.h
diff --git a/webrtc/modules/audio_processing/echo_cancellation_impl.h b/webrtc/modules/audio_processing/echo_cancellation_impl.h
index b2b1090153125f9e4e30a8e32d75aebd9c78e7d5..2abbf01e5a58df583142851fa631a96e162ef494 100644
--- a/webrtc/modules/audio_processing/echo_cancellation_impl.h
+++ b/webrtc/modules/audio_processing/echo_cancellation_impl.h
@@ -12,6 +12,7 @@
 #define WEBRTC_MODULES_AUDIO_PROCESSING_ECHO_CANCELLATION_IMPL_H_
 
 #include "webrtc/base/scoped_ptr.h"
+#include "webrtc/base/thread_checker.h"
 #include "webrtc/common_audio/swap_queue.h"
 #include "webrtc/modules/audio_processing/include/audio_processing.h"
 #include "webrtc/modules/audio_processing/processing_component.h"
@@ -40,7 +41,8 @@ class EchoCancellationImpl : public EchoCancellation,
                              public ProcessingComponent {
  public:
   EchoCancellationImpl(const AudioProcessing* apm,
-                       CriticalSectionWrapper* crit);
+                       CriticalSectionWrapper* crit,
+                       const rtc::ThreadChecker* render_thread_checker);
   virtual ~EchoCancellationImpl();
 
   int ProcessRenderAudio(const AudioBuffer* audio);
@@ -98,6 +100,8 @@ class EchoCancellationImpl : public EchoCancellation,
 
   const AudioProcessing* apm_;
   CriticalSectionWrapper* crit_;
+  const rtc::ThreadChecker* const render_thread_checker_;
+
   bool drift_compensation_enabled_;
   bool metrics_enabled_;
   SuppressionLevel suppression_level_;