Expose Set and Get Recording/Playout sample rate apis

Message:
This is the first cl to add Set/Get Recording and Playout sample rate apis.
In this cl, apis are enabled but returns -1, will add android
implementation in next cl, it's easy for review and coding.

Description:
This CL expose fours voice engine apis,
SetRecordingSampleRate,
RecordingSampleRate, 
SetPlayoutSampleRate,
PlayoutSampleRate. 

BUG=none
TEST=trybots
Review URL: https://webrtc-codereview.appspot.com/626004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@3239 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/voice_engine/voe_hardware_impl.h b/voice_engine/voe_hardware_impl.h
index c801228..9477567 100644
--- a/voice_engine/voe_hardware_impl.h
+++ b/voice_engine/voe_hardware_impl.h
@@ -65,6 +65,11 @@
     virtual int EnableBuiltInAEC(bool enable);
     virtual bool BuiltInAECIsEnabled() const;
 
+    virtual int SetRecordingSampleRate(unsigned int samples_per_sec);
+    virtual int RecordingSampleRate(unsigned int* samples_per_sec) const;
+    virtual int SetPlayoutSampleRate(unsigned int samples_per_sec);
+    virtual int PlayoutSampleRate(unsigned int* samples_per_sec) const;
+
 protected:
     VoEHardwareImpl(voe::SharedData* shared);
     virtual ~VoEHardwareImpl();