Bug 1158931 - Fix static assertion compilation error; r=snorp

Move the destructor for WebrtcAndroidMediaCodec to be protected instead of public.

media/webrtc/signaling/src/media-conduit/WebrtcMediaCodecVP8VideoCodec.cpp

@@ -174,9 +174,6 @@ public:
     CSFLogDebug(logTag,  "%s ", __FUNCTION__);
   }
 
-  virtual ~WebrtcAndroidMediaCodec() {
-  }
-
   nsresult Configure(uint32_t width,
                      uint32_t height,
                      const jobject aSurface,
@@ -507,6 +504,10 @@ public:
     mEncoderCallback = aCallback;
   }
 
+protected:
+  virtual ~WebrtcAndroidMediaCodec() {
+  }
+
 private:
 class OutputDrain : public MediaCodecOutputDrain
   {