Added calls to set and get external echo channels.

Review URL: http://webrtc-codereview.appspot.com/62005

git-svn-id: http://webrtc.googlecode.com/svn/trunk@196 4adac7df-926f-26a2-2b94-8c16560cd09d

src/modules/audio_processing/main/interface/audio_processing.h

@@ -356,6 +356,20 @@ class EchoControlMobile {
   virtual int enable_comfort_noise(bool enable) = 0;
   virtual bool is_comfort_noise_enabled() const = 0;
 
+  // A typical use case is to initialize the component with an echo path from a
+  // previous call. The echo path is retrieved using |GetEchoPath()| typically
+  // at the end of a call. The data can then be stored for later use as
+  // initializer, using |SetEchoPath()|.
+  // Controlling the echo path this way requires the data |size_bytes| to match
+  // the internal echo path size. This size can be acquired using
+  // |echo_path_size_bytes()|. |SetEchoPath()| causes an entire reset, worth
+  // noting if it is to be called during an ongoing call. It is possible that
+  // version incompatibilities may result in a stored echo path of the
+  // incorrect size. In this case, the stored path should be discarded.
+  virtual int SetEchoPath(const void* echo_path, int size_bytes) = 0;
+  virtual int GetEchoPath(void* echo_path, int size_bytes) const = 0;
+  virtual const int echo_path_size_bytes() const = 0;
+
  protected:
   virtual ~EchoControlMobile() {};
 };