Remove VideoCodingModule::InitializeReceiver.

This code is no longer used to reset, so we can just initialize the
object in the constructor.

BUG=4391
R=stefan@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/43249004

Cr-Commit-Position: refs/heads/master@{#9044}

webrtc/modules/video_coding/main/source/receiver.h

@@ -43,7 +43,6 @@ class VCMReceiver {
   ~VCMReceiver();
 
   void Reset();
-  int32_t Initialize();
   void UpdateRtt(int64_t rtt);
   int32_t InsertPacket(const VCMPacket& packet,
                        uint16_t frame_width,